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1079 



TERTIARY FAUNA OF FLORIDA ' ^ 



Section Leptocardia Meek. 

 Leptocardia Meek, Pal. Upper Missouri, p. 172, 1876; C. suhquadrahmi 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 ^m 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 Nemocardiuin. All the 

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

 sculpture, though, as in Lavicardiuni, 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 Chlauiys. Pachycardium should be transferred to 

 the vicinity of Lccvicardium. 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 Lophocardiuin, 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 Papyridca), 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 



