323 



CHARACTERS OF A NEW SUB-GENUS AND 

 CHOANOPOMA FROM CUBA. 



SPECIES OF 



By H. B. Preston, F.Z.S. 



Read 11th Ai^ril, 1913. 



Ramsdenia, u.subgen. 



Shell perforate, cylindrical, the first t^^o whorls mamillary, 

 contiguous, the third widely disjunct, the fourth, fifth, and sixth 

 contiguous except towards the aperture where the last is slightly 

 disjunct, transversely, laininately sculptured; operculum calcareous, 

 with central, depressed nucleus, the outer margin costulate, the inner 

 or depressed portion bearing a raised spiral ridge. 



Genotype: R. mirifica, n.sp. 



The adult shell is generally decollate, and lacks the first three 

 whorls ; thus only immature specimens, as a rule, show the upper 

 distinguishing characters. 



There seems little doubt but that Ramsdenia should be classed as 

 a sub-genus of Choanopoma,^ Pfr., and would in some respects appear 

 to be intermediate between Choanopoma, setisu stricto, and its sub- 

 genera BlcBSospira'^ and Xenopoma,^ both of Crosse. 



It is with great pleasure that I associate the name of my friend 

 Mr. Charles T. Rarasden, the collector, with the above sub-genus. 



\ 





Choanopoma (Ramsdenia) mirifica, n.sp. 

 Shell dextral, cylindrically fusiform, cream-coloured; whorls 6, the 

 first two smooth except in the sutural regiou, where they are strongly 

 and serratedly crenellate, the third whorl loosely disjunct, sculptured 

 only with erect, fine, slightly distant, transverse costulse, the fourth, 

 fifth, and sixth volutions joined except just behind the aperture, 

 angled at the periphery, sculptured with spiral lirse crossed by very 

 wavy, erect, fine, frill-like, transverse costulae arranged in groups of 

 two or three on the fourth whorl, three to four on the fifth, and four 

 to five or six on the last whorl, the interstices being occupied with 

 fine, wavy, scratch-like, spiral striae ; suture deeply incised, coarsely 



^ Zeitsch. f. Malak., 1847, pp. 47, 107. 



■ Journ. de Conch., Paris, vol. xxxviii, pp. 280-2, 1890. 



^ Tom. cit., pp. 282-3. 



