286 PROCEEDINGS OF THE MAT-.VCOLOGrCA.L SOCIETY. 



structural and sj-steniatic, by G. W. Tryon, continued by H. A. 

 I'ilsbry, which is a welcome work and very thorougldy done. The 

 genus Trochomorpha is treated of in Part 33 ; his divisions, I see, 

 c()rres])ond on the whole with mine, particularly in tlie aclcnowledg- 

 nu>ut of Elanford's genus Sivella, on account of the long duct to the 

 spermatheca, but he does not allude to the great dilference in the 

 radula also. But Disciis has surely priority over Videna. 



3. Helix (?) conicoides, Metcalfe. 



The animal in spirit is of a pale ochre colour, with a distinct mucous 

 gland and a short overhanging lobe, unlike the small hidden slit of 

 Sirella castra. The right dorsal lobe is small, the left is naiTow and 

 divided. The duct leading to the anal orifice is barred and spotted 

 with black on a white ground, which in life shows strongly through 

 the shell. 



Odoniopliore (Fig. 4^). — The central tooth rises from a broad 

 base ; is simple, long, narrow, and pointed ; no basal cusps. At the 

 13th tooth the bicuspid form commences, the outer cusp low down — 

 tliis rises gradually ; and the outermost teeth are evenly bicuspid. 



55 : 3 : 10 : 1 : 10 : 3 : 55 

 68 : 1 : 68 



Jaw semicircular, with a central projection (Fig. Ac). 



Generative orgam (Fig. 4). — The penis is large, muscular, with the 

 vm deferens joining it at the posterior end, the retractor muscle being 

 attached a short distance below it. There is no amatorial organ with 

 sagitta amatoria. In three specimens I examined the spermatophore 

 (Fig. Ab) was present; in one case (Fig. Aa) at its place of develop- 

 ment near the junction of the vas deferens, in the other two it was 

 found lower down, and close to the generative aperture (see Fig. 4). 

 It is hard, pointed and solid, triangular in form in front, then coiled 

 on itself, and terminating behind in a long cylindrical sac. In one 

 crushed specimen there were four well-defined spines visible, but their 

 correct position in the perfect animal could not be made out. 



I think it is now shown that Sivella and Discus differ in a sufficient 

 number of characters to be considei'cd subgeneiically distinct. Tliis 

 disposes of a niimber of species that have been put into Trochomorpha. 

 Tlie animals of a great many more wait for examination ; some may 

 not even belong to tbe Zonitida^ at all. Semper places Truchomorpha 

 in the Helicidas. There is a slight difficulty in determining which 

 species is the type ; T. conus, of Java, heads the list of sixteen 

 species in the original description by Albers in 1850. He no doubt 

 at that time considered them of equal value ; the selection of a single 

 type was not then considered of the importance it now is, and it was 

 (juite an accident which species headed the list; but in the second 

 edition of Albers' s work by Yon Martens, the typical species of every 

 g(>nus is indicated, and in this case it is T. trochiformis, Fer., of 

 Tahiti. I have not yet obtained any species from that part of the 

 world. Semper gives a description and figures of the radula of 

 2\ sublrochifonnis, which he places in Videna : this, however, is not 



