366 tellinidce. 



This large and well-known family differs from the 

 Venerida in the pallial tubes being invariably long and 

 separate, the beaks being less recurved, and the liga- 

 ment placed on the smaller side of the shell, and also in 

 having fewer cardinal teeth. The comparative length 

 of the tubes in each individual, caused by their exten- 

 sion or contraction, seems to depend on the will of the 

 animal; sometimes the incurrent, and at other times 

 the excurrent tube is the longer of the two. In families 

 which have these tubes united, there can, of course, 

 be no such inequality. Carpenter has shown that the 

 shells of the Tellinidce are of a solid texture, and that 

 their external and internal layers present appearances 

 of a prismatic cellular structure ; he termed these cells 

 " fusiform," and observed that they were arranged in 

 the two layers in opposite directions. 



The Tellinidce inhabit sand, and occasionally mud, at 

 all depths ; some kinds are littoral. 



Poli proposed the name Peroncea for the animals of 

 the genera comprised in the present family. 



Genus I. GASTRA'NA *, Schumacher. PL VII. f. 2. 



Body oval, tumid and thick : tubes having cirrous orifices. 



Shell equivalve, inequilateral, wedge-shaped, ventricose, 

 decussated by concentric ridges or laminse and longitudinal 

 striae : teeth, one large cloven cardinal and a minute triangular 

 one by its side in the left valve, and two equal-sized divergent 

 cardinals in the right valve; no laterals: imide margin 

 smooth. 



The solitary species which represents this species in 

 the European fauna may be regarded by some as an 

 aberrant Tellina. The generic difference consists in 

 Gastrana having a more decidedly cuneiform and ven- 



* So named from the turgidity of the shell. 



