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TERTIARY FAUNA OF FLORIDA 



fifth a Psathura (only doubtfully admitted by Lamarck), and the sixth a Diplo- 

 donta. The essential feature of the genus as understood by Lamarck was the 

 possession of an internal resilium situated in a fossette between the cardinal 

 teeth instead of at one side of the cardinals, as in Mactra. The species enumer- 

 ated (i, 4, 5, 6) which do not possess this character were, being fossils, sup- 

 posed to have it by Lamarck, who mistook the triangular gap between the 

 divergent cardinals for a fossette. The correction of this error leaves only 

 two species corresponding to the diagnosis. Corbula had been instituted sev- 

 eral years previously, so we are reduced to the single type, Erycina pellucida, 

 as the exemplar of the genus.* In the absence of an exact knowledge of the 

 facts the genus was misunderstood by many of the early writers and was only 

 put on a sound foundation later by the researches of Recluz, Fischer, and 

 Cossmann. It contains a large number of species, especially in the Eocene, 

 when all incongruous elements are eliminated. Nearomya Gabb, as sagaciously 

 supposed by Cossmann, is a true Erycina. The obsolescence of some of the 

 elements of the hinge among the peripheral species renders some subdivision 

 into sections necessary. The most characteristic feature of the group as a 

 whole is the combination of the minute subumbonal cardinals with the long 

 lateral laminae, the latter being most prominent distally. The following ar- 

 rangement is proposed : 



Subgenus Erycina s. s. Type E. pellucida Lam. 



Shell small, somewhat compressed or not very convex, exterior concen- 

 trically striate, smooth, or rarely with partially radial sculpture, sometimes 

 punctate or sagrinate ; hinge with an obsolete external ligament, sometimes 

 hardly traceable, and a well-marked internal resilium which is attached to 

 the shell in an oblique fossette behind the beaks and close to the cardinal 

 border; teeth, normally, one or two minute cardinals and two lateral laminae 

 in each valve, the latter near and sometimes confounded with the dorsal 

 margin of the valve, usually long, low proximally, more elevated distally, and 

 often recurved upon themselves, like a segment of a cylinder; in the right 

 valve sometimes double with the socket for the laminae of the opposite valve 

 between them. Pallial line with a slight insinuation. 



* Froriep in his Neues Syst. Conch., p. 38, 1807, gave an outline of the Lamarckian 

 system in which he named as type of Erycina Lamarck's first species ; but, since this 

 does not agree with Lamarck's diagnosis, while E. pellucida does, Froriep's selection 

 cannot be accepted. This is lucky, as otherwise we should have to use the name Ery- 

 cina for the genus Cyrcna. 



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