TELLIXIDJ3. 247 



nearly equilateral. The Mactras inhabit sandy coasts, burrowing just below the surface. Mr. Alder 

 says that in the island of Arran M. subtruncata is collected at low water to feed pigs on ; they are 

 also eaten by the Starfishes and Whelks. One hundred and twenty-five species are known living. 

 They are world-wide in their distribution, being especially abundant within the tropics. 



The shell of Gnathodon closely resembles that of Cyrena in form, the valves being thick and 

 smooth, and covered with a green epidermis ; the hinge has two teeth and a deep central cartilage 

 pit; the siphonal fold is moderately deep. Sir Charles Lyell mentions that G. cuneatus was 

 formerly eaten by the Indians. At Mobile, on the Gulf of Mexico, it is found with Cyrena 

 carolinensis burrowing two inches deep in mud. The water is brackish, though there is a tide 

 of three feet. The city of Mobile is built on one of these shell-banks. The road from New Orleans 

 to Lake Pontchartrain is made of Gnathodon shells procured from the lake, where there is a mound at 

 the east end a mile long and fifteen feet high, and twenty to sixty yards wide.* 



The genus Lutraria has a very oblong shell, open at both ends ; it has a prominent cartilage 

 pit and two small teeth in each valve ; the fold for the siphons is deep and round ; the foot is large 

 and compressed ; the shell is covered with epidermis. It inhabits the mud of estuaries. Eighteen 

 species are known, widely distributed. 



The genus Anatinella has an ovate shell ; the cartilage is in a spoon-shaped process within the 

 valves ; there are two small hinge teeth ; the pallial line is nearly entire. Three species are living 

 in Ceylon and the Philippines. 



FAMILY XVIII. TELLINIP^E. 



The shell has equal valves, closed and compressed ; the cardinal teeth are two ; the siphonal fold 

 is large ; the foot is tongue-shaped ; the siphons are separate, long, and slender. " The Tellens are 

 found in all seas, chiefly in the littoral and lamina- 

 rian zones ; they frequent sandy bottoms or sandy 

 mud, burrowing beneath the surface ; a few species 

 inhabit estuaries and rivers. Their valves are often 

 richly coloured and ornamented with finely sculp- 

 tured lines." (S. P. Woodward.) 



Genus Tellina. The shell is ovate, oblong, 

 rounded in front, angular behind ; the valves 

 smooth or marked with radiating strise. The most 

 beautifully coloured Tellince are found in the seas 

 of tropical regions. The animals have the power 

 of leaping from the surface by means of their 

 muscular foot. More than 300 species have been 



TELLIXA RAIHATA. 



Genus Gastrana. The shell is triangular, valves 



equal and convex ; there are two cardinal teeth in the right valve and one in the left ; the siphonal 

 fold is deep and rounded. Gastrana bores in mud and clay, and does not move about freely like 

 Tellina. Three species are known from South Africa. 



Genus C-apsula. The shell is ovate, long, open at each end ; it is striated radially ; there are two 

 hinge teeth in each valve; the animal resembles Psammobia, but the siphons are shorter. Four 

 species are living in the West Indies, China, <fcc. 



Genus Psammobiai, " Sunset shell." The surface of the valves is smooth or radiately striated, 

 the siphons very long and slender. They inhabit sand and mud, and range from the littoral zone to 

 a depth of 100 fathoms. A few inhabit British shores, and others with very delicate and beautifully- 

 rayed shells are natives of the Pacific and Indian Oceans, &c. 



Genus Sanguinolaria. The shell is ovate oblong, round in front, attenuated and gaping behind ; 

 the pallial fold is very deep ; the hinge ligament external ; the teeth small, two in each valve ; the 

 siphons very long ; the foot large and tongue-shaped. Twenty species are found living in tho 

 West Indies, Australia, Peru, &c. 



The genus Semele has a shell like a Tellina in shape, with two hinge teeth in each valve, the 

 * " Second Visit to tbe United States," vol. ii., p. 106. f Greek, psammos, sand; lios, life. 



