210 Mr. W. H. Benson on the Cyclostomacea. 



two small Helices of the Western Himalaya reappearing in 

 Sikkim, and a third in the Khasia Hills, together with the 

 little Pupa plicidens, of which a solid variety occurs at Cherra. 

 Helix Castra, B., of Sikkim also recurs in the Khasia Hills* and 

 in Tenasserim ; and Helix delihrata, a Teria Ghat species, ap- 

 pears again in Tenasserim, under Gould's synonym of procum- 

 bens. Helix rotatoria, V. d. Busch, keeps up the correspondence 

 of the Burmese forms with the island of Java to the south of the 

 Equator, where Helix Winteri represents H. Huttoni, Pfr., of the 

 Western Himalaya and Darjiling. 



A continuous chain of Cyclostomacea, gradually modified and 

 diminishing in the number of forms, runs from Borneo to the 

 regions where the Himalaya bids farewell to a subtropical cli- 

 mate ; but of the following genera, viz. Diplommatina, Alycoius, 

 Megalomastoma,Rhaphaulus,Pupina, and Streptaulus, not a single 

 species has succeeded in crossing the sea, or the barrier of the 

 Gangetic plains, to the central or southern mountains of the 

 Indian Peninsula. The Pupiniform type makes an effort to 

 cross the Bay of Bengal, in Registoma, which, in the Nicobars, 

 is associated with Cataulus ; and the latter genus is fully deve- 

 loped in Ceylon, but does not extend to the Indian Peninsula, 

 where Cyc/ophorus, in varied forms, Pteroetjclos, Cyclotus, and 

 perhaps Leptopoma, spread themselves northward. The first 

 two alone attain the banks of the Ganges, at a point within 

 view of the Snowy Peaks which overlook the more productive 

 northern branch of the Malayan stream, along which line, more- 

 over, a Streptaxis is found to reach the Khasia region ; whereas, 

 by the Cingalese route, the genus does not pass beyond the 

 Nilgherry Mountains in Southern India. 



Dr. Pfeiffer has shown himself disposed to include Sowerby's 

 Cyclostoma Cornu Venatorium under the Cingalese genus Aulo- 

 poma, while admitting the absence of the chief character which, 

 apart from the peculiar operculum, distinguishes that genus, 

 viz. the solution of the last whorl. He referred a specimen of 

 C. Helicinum to it in the 1st Part of * Kiistei''s Cyclostomaceen,' 

 and in the 2nd Part figured a shell (plate 49. f. 14-16) under 

 Sowerby's name with doubt. This figure, on comparison with 

 that given in the ' Thesaurus,' cannot be regarded as Sowerby's 

 species. I have always considered that C. Cornu Venatorium, S., 

 must be referred to Cyclophorus ; and a sliell found in Ava by 

 Mr. Oldham, agreeing in every respect with that described and 

 figured in the ' Thesaurus,' except in having the apex white, 



* The Khasia Helix plectostoma, B., common on rocks and trees at 

 Teria Gh^t, has been found by the Messrs. Blanford at Darjiling. 



