MUSEUM OF COMPARATIVE ZOOLOGY. 257 



metaxce, — the shell is translucent white with a single narrow brown band appear- 

 ing in the interspaces between the ribs just in front of the suture; the whorls 

 are shorter, rounder, and less scalar than in C. metaxce, and the four nuclear 

 whorls are dark brown, forming a styliform dark tip to the shell, with a sudden 

 change to the normal color at the junction. The sculpture of the nucleus is 

 composed of concave transverse narrow ripples regularly and closely set, and 

 one or two peripheral fine lines, all of which it requires a good glass to observe. 

 In C. metaxce I find the elongated nucleus white and merging insensibly into 

 the rest of the shell, while in the present variety, which I propose to name 

 tceniolata, the nucleus "appears to be composed of a totally different sort of 

 shelly matter from the adult portion. The specimens average smaller and 

 more slender than C. metaxce of the same number of whorls, and the spirals 

 are rounder and the interspaces less channelled than in most specimens of that 

 shell. 



In examining the specimen referred to by Dr. Jeffreys as presented to him 

 by De Stefanis from the Bay of Naples (P. Z. S. 1885, p. 61, line 18), I find 

 that it is an individual of the form called Bittium abruptum by Mr. Watson, 

 and another tip referred in the Jeffreys collection to " C. angustissimwn Forbes, 

 Jr.," shows the characteristic apex of C. abruptum. It is from Tunis, and was 

 dredged by Captain Nares, in 50-100 fms. 



Cerithiopsis abrupta Watson. 



Plate XX. Fig. 5. 



Bittium abruptum Watson, Linn. Soc. Journ., XV. p. 119, 1880; Rep. Chall. Gastr., 

 p. 551, pi. xli. fig. 4, 1885. 



Habitat. Barbados, 100 fms. Gulf of Tunis, 50-100 fms., Nares. Gulf of 

 Naples (Stefanis), Jeffreys. 



This closely resembles C. metaxce, and is distinguishable by having a low 

 rather large nucleus of two whorls, which has at first a decollate appear- 

 ance. The shell is on the whole smaller and more slender than the genuine 

 C. metaxce, and has, in the specimens I have seen, one less spiral thread than 

 C. metaxce of the same size. 



It seems to me, in the absence of any data as to the soft parts, that this 

 species is better placed next to C. metaxce than anywhere else. 



Family CERITHIIDJE. 



The genus Bittium was mentioned in my Preliminary Report, but further 

 study and better material show that the supposed Bittium yucatecanum belongs 

 to Semper's genus Mathilda. Of genuine Bittium within our region, Bittium 

 altcrnatum Say (as Turritella) is better known as B. nigrum Totten or Ce- 

 rithium Sayi Menke. This creature has a short contractile muzzle, and a 

 narrow, medially grooved, anteriorly truncate foot, like the true Cerithia to 



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