ISOCARDIA. 475 



The fry, vvliicli is very rarely to be met with in cabinets, 

 is very thin, transparent, and of a subcordiform obovate 

 shape. It is of an uniform whitish hue, and remarkable 

 for its somewhat opaline diaphanous yellowish epidermis, 

 which is studded with minute hairs in radiating series. 

 This peculiarity is observable likewise under the lens in 

 well preserved middle-aged specimens. The epidermis in 

 the Mediterranean examples (which do not appear to 

 reach the dimensions of the northei-n shell) is smoother, 

 rather more shining, and of a ruddier cast. 



The following interesting account of the animal and its 

 habits was communicated by the Rev. James Bulwer to the 

 2nd volume of the Zoological Journal. 



" Mantle completely lining the shell, double at the outer 

 edge ; exterior fold divided in front, open at each end ; at 

 the posterior end forming two short siphons or tubes, 

 ciliated at the upper orifices ; colour yellowish white ; mar- 

 gin orange. Foot very muscular, broad, triangular, com- 

 pressed, pointed, orange. Branchiae external, concealed 

 between the mantle and the body. Body soft, completely 

 included within the valves. On being placed in a vessel of 

 sea-water the valves of the shell gradually opened, to the 

 extent represented in the drawing ; the feelers or ciliated 

 fringe of the upper orifice of the mantle moved slowly, 

 as if in search of animalculse. Having remained in this 

 situation about ten minutes, water was ejected with con- 

 siderable force from the lower orifice, which till now had 

 remained motionless. The expulsion of the water appeared 

 to be effected by a sudden contraction of the muscles, be- 

 cause this was never done without the valves nearly closing 

 at the same instant. After a few seconds the valves gra- 

 dually returned to their open position, and remained qui- 

 escent as before, till the water was again ejected with a 



