176 Mr. W. H. Benson on the genus Alycseus, Ch^ay, 



XX. — A Sectional Distribution of the genus Alycseus, Gray, with 

 Characters of six new species and of other Cyclostomidse col- 

 lected at Darjiling by W. T. Blanford, Esq., Geol. Survey. 

 By W. H. Benson, Esq., Retired Bengal C.S. 



The examination of a collection of Darjiling shells, made by 

 Mr. W. T. Blanford, enables me to add several new forms to my 

 previous list of the productions of that rich locality. The num- 

 ber of species now known to me is fifty-four, of which thirteen 

 or fourteen, belonging to Helicidous groups, have been met with 

 elsewhere in the mountain ranges of India. Nearly in accord- 

 ance with a former remark regarding the limited tracts occupied 

 by each particular species of the Cyclostomidse of these regions, 

 only one of the operculated species has occurred elsewhere ; but 

 this shell (Cyclophorus tomotrema, B.) was found, at Pankabari, 

 with an aperture so imperfect, that its identification may be 

 open to a slight doubt. Two Darjiling forms are deficient in 

 the present collection ; these are Cyclostoma Tryblium, B., and 

 a small Helix previously communicated by Mr. Blanford to Mr. 

 Theobald, and forwarded to me for examination. 



The collection is singularly rich in the interesting little genus 

 Alycceus, Gray, which offers six new species, including my un- 

 published^. Otiphorus, received from Mr. H. Blanford in 1857. 

 The Darjiling representatives now amount to nine. Having 

 before me eighteen species out of twenty at present known, I 

 am enabled to propose a more natural grouping of the species 

 than that given by Dr. Pfeiffer in the 1st Supplement to his 

 Monograph, where he divides them into " subturbinate '' and 

 " depressed.^^ The mode of constriction appears to me the best 

 character for the division of the genus into natural sections, and 

 preferable to the form of the shell, or to the greater or less de- 

 velopment of the sutural tube or siphon. Inasmuch as the 

 divisions {Dioryx especially) may be eventually held to possess 

 good generic differences, I shall designate those which are re- 

 moved from the original type by distinct names. 



Sect. 1. Alyccms. Normal group. 

 The last whorl constricted somewhat remotely from the aper- 

 ture, tumid on both sides of the constriction. It contains ten 

 species, including that earliest known, A. gibbus, Per. 

 a. Subpyramidal. 

 gibbus, Fer. Sutural tube variable (from injury?). Cochin China, 

 pyramidalis, B. Tube elongate. Tenasserim. 



b. Globose- or ovate- conical, 

 constrictus, B. Tube very short. Darjiling. 

 Otiphorus, B.^ n. s. Ditto. Ditto. 



Bembex, J5., n. s. Ditto. Ditto. 



