188 AMERICAN JOURNAL 



ON THE LINGUAL DENTITION OF NANINA. 



BY THOMAS BLAND AND W. G. BINNEY. 



An opportunity of examining the lingual membranes of two 

 species of Nanina has brought to light several interesting points 

 of difference from the characters supposed to belong to the genus. 



Dr. Gray (Br. Mus. Cat. 74), referring to Troschel's figure of 

 Nanina retrorsa (Arch, fur Nat. xv. t. 4, f. 6), describes the cen- 

 tral teeth as simple, the laterals as having a broad double base, 

 the marginals with a narrow double base, each of the lobes being 

 bifid. In the species described below, neither centrals, laterals 

 or marginals agree with this description. In general terms, our 

 species may be said to agree with the usual well-known charac- 

 ters of Wyalina or Zonites, with the exception of the marginals 

 being bifid. Thus we find considerable variation in the lingual 

 dentition of the genus Nanina. 



Nanina Calias, Benson, (pi. J 7, fig. 6, 8). Specimens in alco- 

 hol, received from the foot of the Himalayas, have been sent us 

 by Mr. J. G. Anthony, of the Museum of Comparative Zoology. 

 We have extracted the lingual membrane, which is long and 

 broad. The centrals and laterals are arranged horizontally, the 

 former have their reflected apex tricuspid, the latter bicuspid. 

 In this and other respects, the centrals and laterals agree with 

 the usual characters of the species of Ilyalina and Zonites. (See 

 Land and Fresh-water Shells of North America, Part I.) There 

 are ten well marked laterals, beyond which the teeth change rap- 

 idly into the marginals. These last are much more numerous than 

 the laterals, and are arranged in oblique rows; they are simple 

 aculeate teeth, nearly resembling the marginals of Zonites and 

 Hyalina. The recurved portion and the base, however, are both 

 much more thick and less graceful than in those genera, and the 

 recurved portion, instead of narrowing rapidly to an acute point, 

 expands slightly, and is bluntly bifid. 



