288 CYLICHXA. 



posed of imbricating prickly. elements ; gizzard containing 3 equal, 

 oval calcareous plates (pi. 61, figs. 26, 27, C cdhd). Radula with 

 the central teeth small, erect, with bilobed, serrate apices ; laterals 

 large, hooked, with a series of fine denticles near the edge ; uncini 

 small, simple, from 2 to 5 in number on each side (pi. 61, figs. 24, 

 25, C. alba). 



In regard to the several names quoted in the above synonymy, 

 Ihdlina of Risso is clearly preoccupied. Cylindrella Swainson was 

 first acceptably defined on page 326 of the Treatise on Malacology, 

 and is preceded by Cylindrella proposed for a section of Conus on p. 

 311 of the same work, and probably by Cylindrella Pfr. also, pro- 

 posed for a well-known genus of land snails. The name CyUchna 

 of Loven has recently been rejected by Mr. R. B. Newton, on 

 account of the prior Cyl!chnu--< of Burmeister in Coleoptera, and a 

 new name, Bullinelhi, substituted ; but if tbe generic name given by 

 the great Scandinavian naturalist be ruled out, the genus must be 

 given the name of one of the recognized subgenera. 



In the present stage of our knowledge, it is practically impossible 

 to definitely locate many species of small Bulloids, as the shells 

 aff"ord so slight a clue to the modifications of the soft parts. There 

 are, therefore, numbers of forms which can equally well be placed 

 in Cylichna as in the section Cyliclinina of Retnsa. Others might 

 be placed in either Cylichna or Haminea; whilst the distinction 

 between Cylichna and Atys is by no means clear in certain cases. 

 At the same time, it must be clearly understood that the anatomical 

 distinctions between Cylichna, Cylichnina, Haminea, etc., are very 

 great. In these small smooth Bullidte, as in the Zonitoid Helices, 

 the differentiation has been mainly in the soft parts, the shells 

 undergoing but little change. 



Besides this confusion in the genera, there exists at present a 

 semi-chaotic condition of the species ; and so many Cylichnas are 

 inadequately described, so many are still unfigured, that the identi- 

 fication of specimens is often an extremely difficult task. One could 

 spend years of work over these groups of small species ; but as the 

 writer has neither the requisite time or facilities for redescribing the 

 types and figuring them on a uniform and sufliciently enlarged 

 scale, the present account may be considered as simply a digest of 

 the literature of the group. As such, it is believed to be nearly 

 complete. 



