FRONT-GILLED GROUP 



3347 



from Cape Cod northward. It is found fossil in the Coralline Crag. Owing to the 

 variability in the shell, a considerable number of so-called species of Buccinum 

 have been described; but the total of recognizable forms does not probably amount 

 to more than about sixty or seventy. These are mostly Arctic or northern, but a 

 few are known from Japan. Volutharpa is scarcely separable from Buccinum, but 

 the shell is thinner, and the aperture very 

 large. On the contrary, the operculum is 

 minute, that of V, perryi from the Japanese 

 seas a shell about two inches long being 

 only about one-fourteenth of an inch in 

 diameter. Neobuctinum is the Antarctic 

 representative of Buccinum; the single 

 known species occurring at Kerguelen 

 island in the Southern Ocean. The oper- 

 culum differs from that of Buccinum in be- 

 ing somewhat spiral, instead of concentric, 

 and the lingual dentition is slightly differ- 

 ent. Cominella, Cyllene, Tritonidea, 

 Pisania, and Euthria are genera referred to 

 the family Buccinidce, on account of general 

 similarity in the animals, and especially of 

 the radula. They comprise a considerable 

 number of species from tropical and tem- 

 perate localities, but are not of sufficient 

 interest to be further mentioned. We may, 

 however, call attention to the genus Euthria, 

 as a remarkable instance of wide geo- 

 graphical range. The typical species, E. 



cornea, which is very common in the Mediterranean, has also been found on the coast 

 of the island of New Caledonia, eastward of Australia. The genus Phos contains a 

 small number of very beautiful species with highly ornamental cancellated sculpture. 

 On the other hand, the closely-allied Eburna is remarkable for the smoothness of the 

 shell, and the spotted characteristic of the color markings. 



All the members of the family of dog whelks (Nassidce) are comparatively 

 small, none exceeding two inches in length. The animal frequently has the foot 

 which is large bifurcated behind. The radula differs from that of the Buctinidce 

 in having the central tooth curved and finely serrated. The typical genus Nassa 

 comprises an extensive group of small mollusks, which exhibit a considerable 

 amount of variation in form and sculpture; and upon these characteristics many sub- 

 divisions have been proposed. The shells are mostly solid, ovate or turreted, 

 smooth, granulated, or longitudinally ribbed. The aperture has a distinct oblique 

 siphonal notch, the columella is more or less coated with callus, and the outer lip is 

 thickened and denticulate, or grooved within. About two hundred and forty spe- 

 cies are recognizable, of which three are met with in Britain. The majority are 

 found in tropical seas. They often occur in immense numbers, and burrow in sand 



SECTION OF WHEI.K. 

 (Natural size.) 



