ON THE IDENTITY OF PLEGTOPYLIS LEIOPHIS AND 

 P. PSEUDOPHIS. 



By G. K. Gtjde, F.Z.S. 



Read \Wi March, 1908. 



Mr. R. Cairns recently sent me three specimens of Pledopylis which 

 he was i;nahle to identify. Of their origin he knew nothing heyonci 

 the fact that they had been purchased by him at Stevens' Sale Rooms. 

 At first the shells puzzled me somewhat, and I thought they belonged 

 to an undescribed form intermediate between Plectopylis leiophis and 

 P. pseiidopMs, for, while having a more depressed spire than the latter, 

 besides being smaller, the parietal vertical lamina was found to 

 be toothed in outline, a feature supposed to be characteristic of 

 P. pseudophis. This led me again to examine carefully all the 

 specimens labelled P. leiophis in my collection, which had considerably 

 increased in number since first I discussed these structures.' 



Lieut.-Col. Godwin-Austen in figuring and describing P. pseudophis"^ 

 compares it with P. perarcta, with which he states it forms a close 

 link, and Avhile figuring side by side P. leiophis he overlooked the 

 latter' s true affinity with his supposed new species, for while 

 P. perarda is not only invariably smaller and more flattened, and 

 has more convex whorls and a deeper suture, its parietal armature 

 is quite distinct, the vertical parietal lamina not being united below 

 to the second short fold, and its upper horizontal fold descending 

 at first, then ascending, and finally descending again towards the 

 aperture, while in. P. pseudophis this fold runs parallel with the suture. 

 On the other hand, the only charactei^s which appeared to separate 

 P. pseudophis from P. leiophis were the toothed outline of the vertical 

 lamina, the more elevated spire, and the absence of the short fold 

 between the first (upper) long fold and the second shorter one. 

 On examining my other specimens I found, however, that none of 

 these characters is constant, for while some specimens have the 

 elevated spire and the toothed outline of the vertical lamina of 

 P. pseudophis, and possess the short fold between the two other 

 folds, stated to characterise P. leiophis, others, again, have a depressed 

 spire, although the vertical lamina is toothed in a varying degree, 

 being entire in some. I have alreadj^ mentioned when discussing 

 P. leiophis ^ that in a specimen in the collection of the late Dr. W. T. 

 Blanford, and now in the British Museum, the short intermediate 

 fold was absent, and that in an immature specimen in my collection 

 this fold appeared as two short coalesced folds, while the figured * 

 specimen of P. pseudophis possesses this fold also. In another specimen, 



' Science Gossip, n.s., vol. iii (1896), p. 154 et seq. 



2 Proc. Zool. Soc, 1874, p. 610, pi. Ixxiv, figs. 3 and 3a. 



3 Op. cit., V (1898), p. 16. 

 * Loc. cit., p. 17, fig. 77. 



