258 DOLTID^E. 



Synopsis of Genera. 

 Genus DOLIUM, Lam., 1801. 



Shell thin, ventricose, globosely oval ; spire short, whorls with 

 spiral depressed ribs ; mouth verj- large, the lip crenulated, sil- 

 lonated within, columella canaliculated, anterior end of aperture 

 not produced, obliquely, widely sillonated. 



About fifteen species occur in the seas of China, Philippines, 

 Australia, Mediterranean, West Indies, etc. 



The section Perdix, Montfort, 1810, has been used for the 

 separation of species with open umbilicus and (so-culled) simple 

 lip, but the gradual gradation from this form to those with closed 

 umbilicus, and more strongly crenulated lip appears to deprive 

 the group of any real value. Another section, Doliof/sus (pre- 

 occupied by Conrad), has been proposed by Monterosato for a 

 single Mediterranean species, imperforate, with expanded den- 

 ticulated lip. 



Subgenus DOLIOPSIS, Conrad, 1865. 



The figure of the type has a short canal, and appears inter- 

 mediate between Dolium and Pyrula. Two Oregon fossils subse- 

 quently referred to the group by Conrad are very similar to 

 recent Dolium. 



DOLIOPSIS QUINQUECOSTA, Conrad (PI. 5,, fig. 32). Eocene, Miss. 



Subgenus MALEA, Val., 1833. 



Form of Dolium, but the lip thickened, somewhat reflected 

 and strongly denticulated the inner lip with two calloused plicate 

 prominences. Gadium, Link, 1807, is said to equal this jrroup. 



The animal differs from Dolium by its foot being less dilated 

 in front, not angular laterally, and by its branchia?, which are 

 nearly equal. 



Genus PYRULA, Lamarck, 1799. 



Shell imperforate, thin, pear-shaped, spirally ribbed, or decus- 

 sated, terminating anteriorly in a moderate, open canal ; spire 

 very short; lip thin, smooth on the margin. No operculum. 

 Dentition (PI. 6, fig. 38). 



Animal with a very large foot, truncated in front, produced 

 at the front angles, acuminated behind; head and neck narrow 



