J48 



ISOCARDIA oblonga. 

 TAB. CCCCXCl —Jig. 2. 



Spec. Char. Oblong-, anteriorly expanded, smooth ; 

 posterior side very small, the beaks curved into 

 it ; hinge line nearly straight. 



This is a transversely oblong- shell, whose margin is 

 four-sided, the side beneath the beaks is very short 

 and much curved, the others long, and approaching to 

 straight ; it is very gibbose towards the beaks; the shell 

 is very thin. 



Found rather sparingly in the Black Rock, near Dub- 

 lin, from two to four inches wide. It is a boldly formed 

 fossil, and the specimens are generally very regular and 

 well defined ; none, however, have been met with that 

 show enough of the hinge to prove by it that they belong 

 to the genus Isocardia ; — the same observation will also 

 apply to the I. concentrica ; — it is only by their general 

 form that we are led to arrange them both under that 

 genus, the thinness of their shells is rather an objection. 



An Isocardia exactly resembling the Cor is met with 

 in the Crag, and we have the cast of another very similar 

 in Limestone ; but neither, perfect enough for figuring. 



