3352 



THE MOLLUSKS OR SHELLFISH 



in relief upon a differently-colored ground. This family includes the genus Cassis 

 and its subgenera, and the genera Morio and Lambidium. Nearly all the species 

 are from hot regions, but a few occur in Japan and New Zealand; and the well- 

 known Mediterranean Morio tyrrhenus has of late years been dredged living in deep 

 water off the southwest of Ireland. 



The tun shells (Doliidtz] are mostly thinnish and of globose form, sometimes 

 of very large size, and always spirally ribbed and grooved. They have no varices, 

 and are without opercula. The foot of the animal is large, and the retractile pro- 

 boscis long, and furnished with an expanded disc at the end, as in the figured 

 Dolium perdix. The shells of the subgenus Malea, which have the outer and inner 

 lips strongly dentate, form a connecting link with the Cassididce. Nearly all the 



TUN SHEI.L, Dolium perdix. 

 (One-third natural size.) 



species, about fifteen in number, are tropical. Two, however, occur in the Medi- 

 terranean, and several in Japan; Dolium galea, which occurs off the south of France 

 and other parts of the Mediterranean, has a shell eight to ten inches in length, and 

 is the largest gastropod of that region. This mollusk, as well as various species of 

 Cassididce and Tritonidce, are said to secrete sulphuric acid. 



The fig'Shells (Pirula~) have an extensive foot, like Dolium, but the mantle is 

 largely lobed on each side, and reflexed upon the shell. This is of an elongate pear 

 shape, with a short spire and a long canal, and has the surface transversely striated 

 or ridged, or more or less cancellated. There are nine recent species belonging to 

 this genus, which is also found fossil in the Chalk and Tertiary deposits. The 

 genus is included in the Doliidce. 



