284 niOCKEDINGS OF TUK M.VLACOLOGICAL SOCIKTIT. 



collected and sent home so much valuable material. An exami- 

 nation of the history of this species carries one into the ^enus 

 Trochomorpha — Albcrs, 1850; type trochifurmis, 1860, of Tahiti — 

 Avhich is a Pacific Island form ; hence it is very doubtful if 

 the many species placed in it from very far distant countries 

 have any relationship to it. The best account of Trochomorpha, 

 after that by Von Martens in Die Preuss. Exped. Ost-Asien, 1867, 

 is the one by Stoliczka, in the Journ. Asiat. Soc. Bengal, 1873, 

 p. 20. He describes II. castra, Benson, a shell with a wide Indian 

 range, giving all the details of its anatomy, with those of another 

 species, II. timorensis, collected at Pcnang. 



Stoliczka alludes to the work of Von Martens, and the hitter's 

 division of this group into two sections — No. 1, the NIgritella of 

 Albcrs, with its type nigritella, a Pacific Island shell (Marquesas); 

 No. 2, the Videna group, in which its author, Adams, placed 

 H. planorbis and similar shells, like H. castra, etc., all widely and 

 perspectively umbilicated, forming a very easily distinguishable 

 group ; while with them V. Martens associated another very difi'erent 

 set, II. conus, H. conicoides, H. lychnia, etc. H. iernatana, Guillun 

 { = 11 hatchienensis, Pfr.), he placed in Nigritella. 



On referring to the description by IStoliczka of H. castra, Bens., it 

 is seen that it can at once be separated from the discoid shells of the 

 Andamans and Borneo. The generative organs (Pig. 5) are different, 

 the very great length of the spcrmathcca being especially striking. 

 The jaw (Fig. 5rt) and radula (Fig. bb) are also different, particularly 

 the latter, as shown on pi. ii, fig. 9, Journ. Asiatic Soc. Bengal, 1873 ; 

 the tricuspid and central bicuspid laterals being much more like 

 Indian Helicoid forms. The construction of the shell also differs in 

 the manner in which the last whorl grows upon the penultimate one 

 near the suture. These differences are quite sufficient in my opinion 

 to constitute a distinct subgenus, and I accept Vly. W. T. Blanford's 

 genus Sivella for H. castra and its Penang ally, identified by Stoliczka 

 as II. timorensis. Whether this shell from Pcnang is the same in 

 its anatomy has yet to be proved. 



Having examined the anatomy of //. hicolor, from Borneo, and 

 H. trilineata, from Great Nicobar Island, described in detail further 

 on, I find they are in all important respects alike. The radulaj are 

 distinguished by the simple straight-sided central tooth, followed by 

 similar plain median teeth, the laterals being bicuspid. The jaw in 

 trilineata has a central projection. The shells are widely umbilicated, 

 discoid, and sharply keeled. There are slight diffeiences in their male 

 organs, but these are not important. Both species differ in their 

 anatomy from S. castra, Bs., as described by Stoliczka, and I locate 

 this latter species in the subgenus Discus, of Albers— type, H. 

 Metcalfvi, which is a good and distinct one. In the past year I 

 find that Professor Wiegman, of Jena, has described the species 

 II. 2)lanorbis, Lesson, from Sumatra, in a paper, " Beitrage zur 

 Anatomic der Landschnecken des indischen Archipels.," in Max 

 AVeber's zool. Ergebnisse einer Reise im Nederliind. Ost-Asien, iii, 

 8 pis. This is au excellent and most welcome addition to our 



