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animal grows at the anterior end, and therefore the shell at the posterior end is older and thicker. The edge of the mantle at the anterior aperture is very thick and See also:

MUSCULAR

muscular; at the posterior aperture also there is a circular muscle, and here the edge is interrupted by a ventral sinus and is provided internally with a dorsal and ventral See also:

VALVE (Lat. valva, a leaf of a double or folding door, allied to volvere, to roll, as of a door on its hinges)

valve which can be applied to each other so as to See also:

close the aperture.' The living animal buries itself in the sand with only the posterior extremity projecting into the Siphonopodiidae. At the See also:

BASE

base of the head dorsally are a pair of See also:

FLAT (a modification of O. Eng. flet, an obsolete word of Teutonic origin, meaning the ground beneath the feet)

flat tentacular lobes from the edges of which the cephalic filaments or captacula arise. These captacula are of unequal length, highly contractile and extensile, easily thrown off and regenerated. They are ciliated, and their extremities are enlarged and have a small lateral depression in each. The captacula are tactile and prehensile and can be protruded from the anterior aperture of the mantle. The foot is elongated and cylindrical, and can be protruded from the anterior aperture to serve as a burrowing See also:

ORGAN

organ. In Dentaliidae it is pointed at the end and has an oblique projecting See also:

FOLD

fold on either side behind the extremity. In Siphonopodiidae it ends in a disk with papillated margins, and in Pulsellum there is a filament in the centre of the disk. Two retractor muscles pass back from the base of the foot to the dorsal side of the shell. See also:

INTERNAL

Internal See also:

Anatomy.—The cavity within the head leads into a true buccal cavity situated within the body at the base of the foot. This buccal See also:

sac is provided with a dorsal mandible and a ventral radula.

The latter is See also:

SHORT, FRANCIS JOB (1857– )

short and carries five See also:

TEETH (O.E. Eel); plural of tooth, O.E. top)

teeth in each transverse See also:

ROW, JOHN (c. 1525—1580)

row. The See also:

INTESTINE (Lat. intestinus, internal, usually in neuter plural intestina. from intus, within)

intestine is short and forms several loops all situated close behind the foot. The See also:

STOMACH (Gr. vrbsaxos from arbga, a mouth)

stomach is small; into it open a small pyloric caecum and the ducts of the See also:

LIVER (O. Eng. lifer; cf. cognate forms, Dutch lever, Ger. Leber, Swed. lefver, &c.; the O. H. Ger. forms are libara, lipora, &c.; the Teut. word has been connected with Gr. i'prap and Lat. jecur)

liver, paired in Dentaliidae, one on the left only in Siphonodentalium. The anus opens just behind the base of the foot. The liver is placed entirely behind the intestine in the See also:

MIDDLE

middle of the body, and behind it the See also:

REST (O. Eng. rest, reste, bed, cognate with other Teutonic forms, e.g. Ger. Rast, Riiste, rest, and probably Gothic Rasta, league, i.e. resting or stopping place)

rest of the body is occupied by the unpaired gonad. The vascular See also:

SYSTEM

system is very rudimentary. See also:

Heart and See also:

BLOOD

blood-vessels are entirely absent ; the blood is contained in sinuses which have no distinct walls or endothelial lining, and the See also:

PRINCIPAL

principal of which are the perianal, the pedal, the visceral and the pallial. It is remarkable that in Scaphopoda only, among Mollusca the blood-spaces are in communication with the See also:

EXTERNAL

external See also:

MEDIUM

medium: a pair of apertures near the renal openings See also:

lead from the perianal sinus to the exterior and allow the blood to See also:

ESCAPE (in mid. Eng. eschape or escape, from the O. Fr. eschapper, modern echapper, and escaper, low Lat. escapium, from ex, out of, and cappa, cape, cloak; cf. for the sense development the Gr. iichueoOat, literally to put off one's clothes, hence to sli

escape during violent contractions of the body. There are no See also:

SPECIAL

special See also:

RESPIRATORY

respiratory See also:

ORGANS

organs, their See also:

FUNCTION

function is carried on by the internal See also:

SURFACE

surface of the mantle. lia r- Lc See also:

ea From Lankester's See also:

TREATISE

Treatise on See also:

ZOOLOGY (from Gr. Nov, a living thing, and ?byos, theory)

Zoology. a, Anus. la.c, Labial commissure. p.g, Pedal ganglion, with ca, Captacula. Liver. otocyst.

c.g, Cerebral ganglion. m, Mouth, pl.g, Pleural ganglion. f, Foot. o, Orifice leading into po, Posterior orifice of go, Gonad. the perianal sinus. the mantle. in, Intestine. oe, See also:

OESOPHAGUS (Gr. o'lvca=I will carry, and r/)ayeiv, to eat)

Oesophagus. ra, Radular sac. k, Left See also:

KIDNEY

kidney. pa, Mantle. st.g, Stomato-gastric ganglion. The renal organs are a pair of short wide sacs with folded walls lying on either side of the anterior end of the liver. They open to the exterior on either side of the anus. The pericardium being absent, there are no See also:

RENO

reno-pericardial apertures. The See also:

NERVOUS

nervous system resembles that of Gastropoda and Lamellibranchia. A pair of cerebral ganglia See also:

lie on the dorsal side of the oesophagus: they innervate the See also:

PROBOSCIS

proboscis or head and its tentacular lobes and captacula. Close to each cerebral ganglion is a pleural ganglion, and each is connected by a long See also:

NERVE (Lat. nervus, Gr. vevpov, a bowstring)

nerve with the pedal ganglion of the same side, the two connectives of either side being united in the distal See also:

PART

part of their course. The pedal ganglia are situated in the middle of the foot. The pleural ganglia are also united by a long visceral commissure as in Lamellibranchs, and this commissure bears two ganglia lying close beneath the epidermis in front of the anus.

There is also a stomatogastric system arising from the cerebral ganglia. Eyes are absent; attached to the pedal ganglia are a pair of otocysts. They are innervated from the cerebral ganglia. The buccal cavity contains a sense-organ on the ventral side called the sub-radular organ. It consists of ciliated epithelium, beneath which are two ganglia connected with the labial commissure by nerves. The only other sense-organs are the captacula, which are tactile and olfactory. Each contains a terminal ganglion connected with sensory cells in the lateral See also:

PIT (O. E. pytt, cognate with Du. put, Ger. Pfutze, &c., all ultimately adaptations of Lat. puteus, well, formed from root pu-, to cleanse, whence gurus, clean, pure)

pit. The sexes are See also:

SEPARATE

separate. The gonad, whose position has already been mentioned, is divided into transverse lobes; its duct is anterior. and single, and diverges to the right to open into the right kidney as in See also:

PRIMITIVE

primitive Gastropods and Lamellibranchs. Development.-The ova are laid separately and develop in the See also:

sea- A, Ventral view of the animal b, Anterior circular removed from its shell. the mantle. B, Dorsal view of the same. b' Posterior do. C, Lateral view of the same. c, c', See also:

LONGITUDINAL

Longitudinal D, The shell in See also:

section. mantle.

E, Surface view of the shell with e, Liver. gill-tentacles exserted as in f, Gonad. a, Mantle. [life. k, Buccal mass (showing through a', Longitudinal muscle. the mantle). a", Fringe surrounding the an- q, Left nephridium. ter i or opening of the s', See also:

CLUB (connected with " clump ")

Club-shaped extremity of the mantle-chamber. foot. al", The posterior appendix of the w, w', Longitudinal blood-sinus mantle. of the'mantle. of muscle muscle of aperture of the mantle cavity is See also:

WATER

water, so that the posterior both inhalant and exhalant. The head is situated on the dorsal side of the body anteriorly within the anterior aperture of the mantle, from which it cannot be protruded. It is a small somewhat cylindrical See also:

PROJECTION

projection with the mouth at its anterior end. In the Dentaliidae the mouth is surrounded by eight small lobes, but these are absent in the i For a discussion of" its relationship to the other classes of the Phylum see MOLLUSCA. water.

One large See also:

CELL (from Lat. cella, probably from an Indo-European kal —seen in Lat. celare, to hide; another suggestion connects the word with Lat. cera, wax, taking the original meaning to refer to the honeycomb)

cell, or megamere, remains for some See also:

time unsegmerited but is finally segmented and forms the endoderrti cells which are invaginated. The gastrula thus formed has a large blastopore, which is at first posterior but afterwards gradually moves towards the anterior end of the ventral surface. The velum is See also:

PECULIAR

peculiar, being reflected backwards ovei the body and bearing, besides an apical tuft, three or four rings of See also:

CILIA (plural of Lat. cilium, eyelash)

cilia. The shell-gland is formed on the dorsal surface, and the mantle arises as two lateral lobes which afterwards unite by their ventral edges to form the tubular mantle of the adult. The anus is not formed till a very See also:

LATE

late See also:

period of the development. The foot arises as a prominence on the ventral surface and grows forward, and at the end of five or six days the velum atrophies and the foot becomes the organ of locomotion; the animal then ceases to swim and sinks to the bottom. Habits and See also:

DISTRIBUTION (Lat. distribuere, to deal out)

Distribution.—Scaphopoda feed on the lowest marine organisms such After Kowalewsky, in Ian_ as Diatoms, See also:

PROTOZOA (Gr. 7rpwros, first, and i'woe, living thing)

Protozoa, &c. There are 15o See also:

TASTE (from Lat. taxare, to touch sharply; tangere, to touch)

taste's T,eatex on zoology. living and about 275 known fossil See also:

SPECIES

species. most abundant from the Cretaceous aspect. onwards. I, Foot. II, mantle. See also:

CLASSIFICATION (Lat. classis, a class, probably from the root cal-, cla-, as in Gr. icaMce, clamor)

Classification.

— Fam. I. Dentaliidae. Foot conical with a laterally See also:

EXPANDED

expanded and dorsally interrupted circular fold. Shell curved with greatest See also:

DIAMETER (from the Cr. &a, through, µErpov, measure)

diameter at anterior aperture and diminishing gradually to posterior. Dentalium: posterior aperture of shell entire, without incision. Antalis : posterior aperture with short incision. Fissidentalium: posterior aperture with long fissure on ventral side; abyssal. Fustiaria. Schizodentalium: ventral border of posterior aperture with a See also:

SERIES (a Latin word from serere, to join)

series of small holes in a straight See also:

LINE

line. Heterochisma. Fam.

2. Siphonopodiidae. Foot expanded distally into a symmetrical disk with a crenate edge or See also:

SIMPLE

simple and vermiform without well-See also:

DEVELOPED

developed lateral processes; shell often contracted towards the anterior aperture. Siphonodentalium: foot ending in a median disk without a median appendage. Cadulus. Dischides. Pulsellum: terminal disk of foot with a median appendage. Entalina. See F. J. H. Lacaze-Duthiers, " Histoire de 1'organisation et du d6veloppement du Dentale," See also:

Ann.

Sci. Nat. Zool. (4), vi., vii. (1856-1857); A. Kowalewsky, " Etude sur 1'embryog6nie du Dentale,' Ann. Musee d'Histoire Natur. (Marseille, Zool. I. 1883); Boissevain, " Beitrage zur Anatomie and Histologie von Dentalium," Jenaische Zeitschr. xxxviii. (1904); See also:

Paul Pelseneer, Mollusca; Lankester's Treatise on Zoology, pt. v. (1906).

(J. T.

End of Article: SCAPHOPODA

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