236 PROCEEDINGS OF THE ACADEMY OP [1893. 



features have been indicated above and will not be repeated here. 

 Owing to the kindness of several conchologists, I have had living 

 examples of a number of species — V.putchella, excentrica, costata, par- 

 vula, alb\da,perspectiva — and I have, besides observing the animals, 

 examined the jaw and radula, necessarily deferring further anatomi- 

 cal studies. 



The foot is small in proportion to the shell, being scarcely as long 

 as the diameter of the latter in the species seen. It is colorless, 

 translucent, as is also the head, so that the internal parts are seen 

 rather indistinctly from above — the jaw, buccal body, oesophagus, 

 with morsels of food and numerous minute air bubbles at times 

 passing it, and even the cerebral ganglia being observable with a 

 good lens. A fine, raised median line extends from the head over 

 the neck. A very fine but distinct line makes a narrow margin 

 or seam above the longitudinal edge of the disc or sole, which 

 shows about 8 to 10 distinct crenulations on either side from head to 

 posterior end. The raised parts are separated by very fine lines, 

 grooves or hyaline septa, which, on the posterior part, have some- 

 what the appearance of an inverted honey-comb, as the septa are 

 impressed. At the tail a slight groove, like a rudimentary mucous 

 pore, seems to be present. I could not determine distinctly separa- 

 ted or defined longitudinal areas in the sole, so that there is no true 

 locomotive disc as described by W. G. Binney, the whole sole being 

 probably comprised in such a disc, since the lateral parts are want- 

 ing, as in many Hyalinia, etc. The locomotive waves or undula- 

 tions extend over the whole width of the disc, and even on the mar- 

 gin above, succeeding each other rapidly and often somewhat irregu- 

 larly, advancing from the posterior end, about five at the same time. 

 They were seen when the animal was retiring in the shell and only 

 the posterior part of the foot still projecting and not attached to 

 anything. In the sole are seen numerous very small white dots, 

 such as are found in almost all our land and fresh water Gastero- 

 poda. 



The eye-peduncles are slender, very little if at all thickened at the 

 ends, glassy, with very finely granulated surface ; inferior tentacles 

 short but distinct. There are two rather large horizontal flaps or 

 lappets at either side of the mouth, but their margins are not cren- 

 ulated as in Acanthinula harpa. In several species, such as pul- 

 chella, excentrica, albula, I found the edge of the mantle slightly 

 colored with a rusty pigment at the periphery, but varying in the 

 different forms ; probably it will be found in all species. 



