440 MARINE INVERTEBRATES 



GENUS Cardita 



C. borealis. A very common species north of Cape Ann, reported 

 also in deeper water as far south as Hatteras. It is a solid, obliquely 

 heart-shaped shell, with beaks elevated and turned forward. It has 

 about eighteen to twenty rounded radiating ribs, 

 which are broader than the grooves between 

 them. The epidermis is rusty-brown. The hinge 

 is strong, with two prominent teeth ; the mar- 

 gins of the shell are strongly crenulated within. 

 Length one inch ; height about the same. This 

 is not strictly a between-the-tides species, but 

 its valves are often cast upon the beaches. Fine 

 specimens may be obtained by dredging at Bar 

 Harbor or Eastport. 



C. floridana. A very common Floridian 

 species. Its seventeen or eighteen ribs are very 



Cardita borealis, natural size. * -i j j i 0.1. 



heavy, and are rendered nodulous by the numer- 

 ous bluntly raised scales upon them. The shell is lengthened, and has a 

 well-defined lunule and an external ligament. In color it is yellowish- 

 white, with purple markings when young. Length one inch ; height three 

 fourths of an inch. It lives in sheltered bays; detached valves are 

 often found cast upon the beach. 



FAMILY ASTAETIDJE 



GENUS Astarte 



Notwithstanding their rather small size, there is a trimness 

 about the shells of Astarte which, taken together with their 

 rich chestnut epidermis, makes them very interesting and desira- 

 ble additions to the cabinet. The family is one of cold-water 

 range, with a few representatives on the New England coast. 

 Live specimens are not easily captured, for they live in deeper 

 water than one would care to wade in, nevertheless they are fre- 

 quently cast upon the beaches after storms. The animal has a 

 very short efferent siphon, large labial palps, and very obliquely 

 placed gills. Not more than twenty living species of Astarte are 

 known, and all of them belong in, or are wanderers from, polar 

 seas. Fully three hundred fossil species of this genus have been 

 described from Mesozoic rocks in all parts of the world. The 

 question naturally arises whether in these its dying days Astart* 1 

 has sought colder waters in which to pass its remaining existence, 

 or whether climates have changed. The fact that such strictly 



