coli.inge: non-operculate Land and freshwater molluscs. 79 



In the form B the apex is much higher than in A, and the 

 last whorl exhibits a somewhat prominent keel. In addition to 

 the band below the keel, there is a broad incipient band above ; the 

 whorls are more convex than usual and the shell thicker. 



In the form C both apex and whorls are flattened, there is very 

 little keel on any of the whorls, and an incipient band above the keel 

 only ; the shell is much thinner than either A or B. 

 Internal Structure of the Animal. — Alinientary Canal. No 

 differences of any importance were found in the intestinal tract. In 

 an example of form C the long straight oesophagus is followed by a 

 wide crop, over which a pair of large salivary glands lie, fused in their 

 mid-dorsal line. Posterior to the crop is a short tube-like portion 

 which passes into the large sac-like stomach, which is coiled upon 

 itself, the posterior portion exhibiting a well marked constriction 

 which separates the terminal portion from the main cavity. The 

 remaining part of the intestine is a simple wide tube, which makes a 

 bend backward over the region of the stomach, and then again forward, 

 traversing the side of the pulmonary cavity. 



'File Generative Onjans (PI. iv, figs, 16-19). — In the form A there 

 is a large vestibule into which the penis opens on the right side. This 

 latter is a long muscular organ for half of its length, then coiling upon 

 itself, it becomes a narrow tube-like body, and making a further sharp 

 turn upon itself it joins the epiphallus, from here a short diverticulum 

 is given off which terminates in a fine hook-like process (PI. iv, fig. 16). 

 The epiphallus is a short tube expanding at its distal end to form a 

 bulbous, sac-like, terminal portion, the kalk-sac, to which the retractor 

 muscle of the penis is attached. The vas deferens joins the epiph- 

 allus just belo.v the insertion of the muscle, and is a long fine tube 

 looped around the vagina. All around the proximal portion of the 

 vagina, a series of short oblic^ue muscles bind this organ to the ventral 

 body wall. The vagina is wide and sac-like in this region, but bending 

 to the right it soon becomes tube-like. The receptaculum seminis is 

 small and its duct short. Inserted in the distal wall of the recepta- 

 culum seminis is a short stout muscle, differing in this particular point 

 from the condition described by Godwin-Austen (13, p. 32). The free- 

 oviduct exhibits a constriction about its middle, and then gradually 

 becoming smaller joins the oviducal portion of the common duct. 

 There is a large conspicuous dart-gland, the actual dart-sac being very 

 small and containing no true dart, this latter being represented by a 

 short, broad, muscular papilla, on the summit of which there is a 

 small, pointed, horny-looking body (PI. iv, fig. 17). 



In the forms B and C the generative organs were very similar to 



