58 DR. GWYN JEFFREYS ON THE MOLI.USCA OF THE [Jan. 20, 



I am now inclined to separate Triforis from Cerithium by reason of 

 the differences in the apex or embryonic part of the shell and in the 

 former having a short basal canal instead of a mere groove or notch. 

 The spire of Triforis is finely pointed, in Cei-ithium it is blunt. In 

 Triforis the apical whorls are much narrower in proportion, and are 

 closely striated lengthwise. In Triforis the canal is small and nearly 

 if not quite closed, as in Murex ; in Cerithium the groove or notch 

 is comparatively large and quite open. According to Meyer and 

 Mobius there is also a characteristic distinction between the animals 

 and odontophores of the two genera. The snout or proboscis in 

 Triforis &nA CenYA/o^sis is retractile, while in Ce?77^?"Mm it is contractile. 

 The radula of T. perversa contains abo\it 26 transverse and short 

 denticulated plates. Triforis appears to be congeneric with Cerithi- 

 opsis, and to belong to the same family. When the shells of 

 T. perversa and C. tubercularis are exhibited one before a mirror 

 and the other not, it will be seen that almost the only differential 

 character consists in the lower or basal portion of the mouth being 

 more closed in the Triforis than in the Cerithiopsis. 



Seguenza and Monterosato regard T. perversa and T, adversa as 

 distinct species because the former is larger than the latter. I cannot 

 agree to their separation on those grounds, and I am not aware of 

 any other difference. Size seldom if ever constitutes by itself a 

 specific character. Professor Stossich kindly gave me a specimen 

 which is more than an inch long besides the apical whorls, which had 

 disappeared, and another specimen which, although quite perfect, was 

 scarcely a line or the tenth part of an inch in length ; both specimens 

 were from the Adriatic. Besides Murex adversus of Montagu there 

 are many other synonyms. 



Cerithium nigrocinctum of C. B. Adams, from the North-Atlantic 

 coasts of the United States, is closely allied to the present species, 

 if it be not the same or one a variety of the other. 



2. Triforis aspera\ Jeffreys. ^^Plate VI. figs. 7, 7a.) 



Shell elongated, rather solid, nearly opaque and glossy : sculpture, 

 rows or bands of small tubercles (18-20 on the last or bottom row), 

 which arise from the mutual intercrossing of longitudinal and spiral 

 striae ; of these rows there are usually three on the last whorl above the 

 periphery, and the same number on several of the succeeding whorls 

 and afterwards two only ; each of the apical whorls (3 or 4) is closely 

 striated lengthwise and encircled by two spiral lines ; the periphery 

 is defined by a rather strong ridge, a little below which is another 

 ridge, besides a shorter and smaller one at the base ; the tubercles 

 which compose the lower two rows are larger and more prominent 

 than those of the uppermost or third row : colour pale yellowish, 

 with a faint tinge of brown ; apical whorls dark brown : spire taper- 

 ing to a fine point ; apex pinched-in and narrower than the rest of 

 the spire: whorls 21-22, compressed, gradually enlarging; the last 

 equals only from ^ to ^ of the shell : suture slight, indicated by the 



' Rough. 



