30 BIVALVES —CARDIUM. 
the Cardia to be separated into three divisions, and 
those divisions into families. 
Specimens of this shell are found in almost every 
sea, and some, though rarely, at the mouths of the 
rivers Tees, Thames, &c. 
This genus has been named Cardium from the re- 
semblance which its species bear to a heart (kapdia). 
Division 1.—Heart-shaped, valves compressed, umbones alter- 
nating. 
Scientific Name. Locality. Common Name. 
Cardissa -+-++-++ East Indies --+++++++++- Venus’s Heart - 
Humanum -: --- East Indies «---+--++-++- Concave----do -- 
Roseum ---*-e«-=« Malay Coast --+sseeecere Rosemeniciones do -- 
Monstrosum ---- South Sea Isles --------: Recurved- --do -- 
Diviston I1.—Sub-cordate, longitudinally ribbed. 
One of the most rare species of this division is the 
C. costatum, which has rows of white, hollow, elevated 
ribs, situated at regular distances, proceeding from 
the umbones to the margin; and the spaces between 
them are, in perfect specimens, of a fine dark brown 
color. 
The C. fragum and C. unedo differ from the other 
species of this division, their ribs being armed with 
small crescent-shaped scales. 
Famity 1.—Having a crescent shaped cavity beneath the umbones. 
Retusum «-«+-<- of) ANCIG terocce steicinc clsisjelaie Diana's Heart - -- 
