244 



NATURAL HISTORY. 



The shell in the genus Lucina is white, the umbones of the valves small and compressed. The 

 margins of the shell are smooth or finely crenulated ; the ligament is concealed, the hinge teeth are 

 lateral. The foot is often twice as large as the animal. 



The Lucince occur in tropical and temperate seas, on both sandy and muddy bottoms, from low 

 water to near 200 fathoms. 



In Corbis the valves of the shell are elegantly sculptured concentrically, and the margins finely 

 toothed within. Five species occur in the Indian and Pacific Oceans. In Diplodonta the shell is 

 very like Lucina,, but with a rather long double ligament, and two hinge teeth. Their distribution 





I, CAKDIUM EDVLE; 2, CARUIUM ECHIXATVM : 3, MYA AIIEXAKIA ; 4, CYTHEREA CHIONE. 



is world-wide. Ungulina has a more oblong form than Diplodonta, with a short ligament and thick 

 epidermis. It burrows in coral, and is found in Senegal and the Philippines. The minute orbicular shell 

 of the genus Kellia is very thin. The animal creeps freely, and fixes itself by a byssus at pleasure. 

 One species (K. rubra) is found in crevices of rocks at high water ; others range to a depth of 

 200 fathoms in Norway, New Zealand, and California. Genus Montacuta, another small form, walks 

 freely on a large and broad foot, and attaches itself to the spines of the Purple-heart Urchin ; 

 others burrow into the valves of dead shells. Lepton has a thick tapering foot, forming a creeping 

 disc. The mantle extends beyond the shell, bearing a fringe of filaments. Genus Galeomma has a 

 thick fibrous epidermis. The foot is long and narrow, with a flat sole. It spins a byssus, which it 

 breaks at will, and creeps about like a snail, spreading out its valves nearly flat. 



