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TERTIARY FAUNA OF FLORIDA 



Section Leptocardia Meek. 



Leptocardia Meek, Pal. Upper Missouri, p. 172, 1876; C. subquadratum Evans and Shu- 

 mard. Cretaceous. 



Shell small, thin, with the form of Protocardia s. s. with the sculpture obso- 

 lete, and the pallial line doubly sinuous near the anterior adductor scar. 



I have cited the above sections indicated by Meek, though I am very 



doubtful of their value. I find the minute tuberculations, which sometimes 



are seated on the ribs and sometimes spring from the channels, are extremely 



fugitive, and it is often difficult to decide even in recent specimens whether 



they have been provided with tubercles or not. Consequently I am disposed 



to unite Nemocardium with Protocardia s. s. Moreover, I find, in examining 



many specimens of recent Protocardia, that in a large proportion of them 



an irregular sinuosity appears in the posterior part of the pallial line, as figured 



by Meek for Leptocardia, but it is not constant in the same species, and is 



probably one of those individual irregularities which have no systematic value. 



Therefore I should let Leptocardia share the fate of Nemocardium. All the 



Protocardias have on the anterior part of the shell both concentric and radial 



sculpture, though, as in Lcevicardium, it may be almost imperceptible. The 



slight variations which will result in radial, concentric, or reticulate sculpture 



on this part of the shell can therefore be held to have hardly more than 



specific importance. The anterior laterals in Protocardia invariably spring 



from the umbonal cavity ; in many forms the posterior laterals, especially in 



the left valve, show signs of obsolescence ; and the dorsal margin of the right 



valve exhibits a tendency to overlap the corresponding margin of the opposite 



valve, as often occurs in Chlainys. Pachycardium should be transferred to 



the vicinity of Lcn'icardium. The spinules next the anterior border of the 



posterior area in Protocardia often fuse together to form a low crest or keel, 



much as in Lophocardium, but this formation is so excessively fragile that 



even in living specimens it is only represented by fragmentary portions of the 



original. 



Subgenus LOPHOCARDIUM (Fischer). 



Lophocardium Fischer (as section of Papyridea), Man. de Conchyl., p. 1038, 1887; C. 



Cumingi Broderip. 

 Lophocardium Dall, Nautilus, June, 1889, p. 13; Proc. U. S. Nat. Mus., xii., No. 773, p. 



264, 1889. 



Shell resembling Protocardia but gaping behind, with the keel bordering 



