SCAPHOPODA. 



(fig. 506). The body possesses a saccular mantle, like the shell open 

 at both ends, and a trilobed foot ; the foot is protruded through the 

 larger of the openings of the shell from the anterior opening of the 

 mantle, the margin of which is thickened. A separated cephalic 

 region is not present, but there is an egg-shaped projection in the 

 mantle cavity, at the apex of which is placed 

 the mouth, surrounded by eight leaf -like labial 



appendages. 



The buccal armature con- 

 sists of a lateral (right and 



left) rudimentary jaw, and a 



tongue beset with five rows of 



plates. 

 The alimentary canal is 



divided into a buccal cavity, 



oesophagus, stomach with large 



liver, and an intestine, which 



after several coils closely 



pressed together, opens behind 



the foot into the middle of the 



mantle cavity. 

 The circulatory organs are 



reduced to two mantle vessels 



and a complicated system of 



wall-less spaces of the body 



Respiration is effected by 

 the surface of the mantle and 



PIG. 506. Dentalium 



Tarentinum (after Cavity. 

 Lacaze- Duthiers). 

 Animal without 

 shell from right 



side P, foot; Mt, also b the filif orm tentacles, 



circular muscle of . J 



mantle; Jf,iongi- which arise from two ridges C 



tudinai ^scie ; / cerv j ca i co n ar \ behind the FlG - 507 - Larva of Denta ~ 



&r, giiis ; J.M, KI [- iium ( a f ter Lacaze-Du- 



ney; L, liver; &, head-like buccal prolongation. thiers) a young larva 



ative gland. ^ ^ ^ ^ fi t ^^^ of 



shell (S). b, Older larva 



rectum, and opens by two openings placed on seen from the dorsal sur- 

 the right and left of the anus. face ; T ' tentacle Collar 5 



G-ff, cerebral ganglion; 



ihe nervous system consists of three groups eg , oesophagus; L, liver. 

 of ganglia, of which the pedal ganglion bears two otocysts. Eyes are 

 absent. The numerous ciliated tentacles serve as tactile organs. 



The Scaphopoda are dioecious. The ovaries and testes are un- 

 paired finger-shaped lobed glands, which are placed behind the liver 

 and intestine, and open to the exterior with the right kidney. 



