SCIENCE-GOSSIP. 



VARIETIES OF ISOCARDIA COR. 



>v F W W tton, M.C.S. 



"VJO varieties of It . or, L., are given in the 



list of British marine shells published by 

 Mr. Somerville, in 1SS5, neither — so far as I am 

 v ;:t — have any been described or figured since 

 that time. 



During the past four years it has been my good 

 fortune to examine something like four hundred 

 specimens which -were dredged in various localities, 

 and I now give the results of my observations, and 



brown or mottled brown and green epidermis, and 

 is really a very striking and elegant object. In 

 adult individuals the epidermis is more or less worn 

 or damaged, and in very old shells entirely gone, 

 so that the valves present a worn and rough 

 appearance. 



Isocardia cor has always borne the reputation of 

 being a somewhat rare species, and good specimens 

 are looked upon by a collector as an acquisition to 



Right v.-.:. - : Isocardia co:- . 

 •Fig. 1. Type. Fi_- 2 ■ ■:. 2), quadrant Fij ; var. ±), q : Fig. 4 1 pha ..:: Fig j (var. 5 



also describe and figure the varietal forms I found 

 amongst them. With such a large number it would 

 be possible — were every slight mutation considered 

 — to create a great many varieties, but to avoid 

 confusion or misconception in the future, I have 

 limited my descriptions to those forms only which 

 are well defined departures from the type shell. 

 Of colour changes I have taken no notice. 



The Isocardia reaches its greatest perfection when 

 about half-grown : it is then clothed with a rich 



his cabinet. The rarity however, consists more 

 in the difficultv of obtaining them than in an 

 absolute scarcity of the molluscs themselves. 



The Isocardiae are gregarious and pass a some- 

 what sedentary existence. They lie partially buried 

 in the mud or sand at depths varying from twenty 

 to sixty fathoms, with the ventral margin upper- 

 most. The hardened condition of the mud which 

 fill the hollows of the umbones indicates that the 

 animals remain stationary, for were they free- 



