454 J. F. ILLINGWOETH, 



object on which it is moving. In the laboratory they crawl up the 

 perpendicular glass sides of the aquarium, and it requires considerable 

 force to displace them. The foot, like the mantle, is exceedingly 

 vascular, and many of the capillaries extend so near to the exterior 

 surface that the injection mass may break through if too much pres- 

 sure is applied. The crawling surface is almost an orange yellow 

 during life, while the sides of the foot as far up as the epipodium 

 are black, resembling in general appearance the outside of the mantle. 



The head, well marked in this genus, is attached to the body 

 by a short, broad neck, and both, like other exposed portions of the 

 body, have the dark coloring. On the anterior lateral angles of the 

 head are the tentacles (Plate 31, Fig. 1 T), which are very contrac- 

 tile and in preserved material are seldom more than one-half their 

 normal length. At the base of each and just back of it is found the 

 ocular tentacle or tubercle (Fig. 1 E). Both of the latter are very 

 dark colored, but by pushing the tubercle back, a small, whitish patch 

 will be seen on the surface toward the tentacle, and almost at the 

 bottom of the angle between them. This is the unpigmented layer 

 over the eye, which is better seen in sections of this part. On the 

 ventral anterior part of the head is the mouth (Fig. 11 Mo) sur- 

 rounded by the slightly protrusible lips upon whose inner edge there 

 is a fringe of brush-like projections (Fig. 11 to) with their distal 

 ends finely divided into almost hair-like branches. The chitiuous 

 jaws can seldom be seen from the outside as they are withdrawn be- 

 tween the lips, except when the animal is feeding. 



Digestive system. The jaws (Fig. 11 J) are rather soft 

 compared with many other gastropods. They are situated on the 

 sides of the oral opening and are connected at their anterior edges 

 by muscular fibers which attach to the wall of the upper lip. Their 

 posterior edges are free and more chitinous. They work in opposition 

 to the radula, the food passing between them. Above and in front 

 of the oral cavity are the yellowish sugar glands (Fig. 6 Sg), which 

 empty their secretion into the anterior part of the mouth, where it is 

 mixed with the food in the process of trituration. On the anterior 

 floor of the mouth cavity a short piece of the radula is seen (Fig. 6 

 Rad), which extends into the radula tube which runs beneath the 

 floor. Back of this a long tongue-like or palp-like projection (Fig. 6 

 Lp) extends to the opening into the pharynx. The roof of the mouth 

 terminates in a similar palp-like organ (Up). These elevations by 



