450 Mr. W. T. Blanford on the Classification of 



to the tubes in other genera of the Cyclophorida. There can 

 be no doubt that the " wing " in Pterocyclos is a rudimentary 

 tube, although no portion of the animal has been observed to 

 correspond with it. 



The species of this genus may well be distinguished into two 

 sections. 



1st. Those inhabiting the Indian peninsula and Ceylon, 

 viz. : — 



P. rupestris, Bens. Bengal, Behar, Orissa. 



P. bilabiatus, Bens. Hills of South India (base). 



P. nanus, Bens. Nilgiri Hills. 



P. Cumingi^, Pfr. Ceylon. 



These are all characterized by their very convex opercula. 



2nd. The Burmese forms — 



P. parvus, Pearson. Assam and Arakanf. 



P. pullatus, Bens. Pegu. 



P. , n. sp. Thayet Myo, Pegu. 



Also, probably, P. cetra, Bens., from Molmain, and P. Albersi, 

 Pfr., from the Khasi Hills. In these the operculum is nearly 

 flat, while the wing of the peristome is much less developed 

 than in the forms of the Indian peninsula. No species have as 

 yet been obtained from the Himalaya. It is worthy of note 

 that the Indian species with the least-convex operculum and 

 smallest wing is the Nilgiri P. nanus, Bens., thus affording an- 



* I am doubtful whether P. Cingalensis, Bens., be more than a variety of 

 P. Cumingi, Pfr. The duphcation of the peristome is frequently a character 

 depending upon the age of the shell, which, of course, may vary in speci- 

 mens collected at different periods of the year. Moreover, which of the 

 Cingalese species is P. Troscheli, Bens. ? Probably P. Cumingi or P. bifrons, 

 Pfr., which may possibly be only varieties of one species. P. Troscheli was 

 described from a drawing, at a time when the fauna of Ceylon was almost 

 completely unknown. This has changed, and the land-MoUusca of Ceylon 

 are now far better known, and have been much more largely collected than 

 those of many parts of India ; and it is very improbable that the species 

 has been overlooked. Descriptions of species from drawings, unless those 

 drawings have been made by persons intimately acquainted with the critical 

 distinctions of allied species, are never satisfactory ; and when, as in this 

 case, three or four other species have been subsequeutly described from 

 the same geographical area, differing from that first named and from each 

 other in minute characters which would infallibly be overlooked by an 

 ordinary observer, it is very improbable that all are really distinct. It is 

 to be hoped that some of the numerous collectors of Ceylon shells may 

 possess specimens of a Pterocyclos from Trincomalee, which would go far 

 towards deciding the question. 



t Specimens of a Pterocyclos which I found in Arakan, at Akyab, and 

 of which a flatter variety occurred further south, near Tongoop, agree 

 generally with the description of P. parvus. The operculum is plano- 

 concave within (the central boss being very slightly prominent) and nearly 

 flat without, with free lamellar edges to the whorls. 



