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TERTIARY FAUNA OF FLORIDA 



less developed laterals and an evenly rounded posterior end. I may add that 

 Liothyris Conrad (not Douville), described as a subgenus of Linear ia, is quite 

 distinct, and its connection with any of the Tcllimdcc is very doubtful. 



B. With tzvo lateral lamina in the right valve, one or both of those of the left 



valve absent or obsolete. 

 Subgenus Elliptotellina Cossmann, 1886. Type Tellina tellinella Lamarck. 



Shell small, subequilateral, convex, with the extremities rounded, the pos- 

 terior not compressed or folded ; hinge with a moderate nymph and ligament, 

 two laterals in the right valve, none in the left ; sinus free, short, rising 

 obliquely from the pallial line ; external sculpture concentric with a tendency 

 to reticulation near the ends by radii from the umbones. Lower Eocene of 

 Paris to recent fauna. 



This remarkable little shell resembles an Ervilia externally, and is quite 

 destitute of some of the most characteristic features of Tellina, to which it 

 is linked by Herouvalia, which has a more fully developed hinge and posterior 

 truncation. Recent species occur in the warm temperate waters of both coasts 

 of North America. 

 Subgenus Pseudarcopagia Bertin, 1878. Type Tellina decussata Lamarck. 



Shell subequilateral, moderately convex or somewhat compressed; the 

 extremities rounded, with no flexure ; hinge with two right but no left laterals ; 

 valves rounded or ovate ; sinus high, partly confluent below ; external sculp- 

 ture reticulate. Tropical, especially Austral seas. 



These forms make a strong contrast with the other Tellinas, owing to their 

 conspicuously reticulate sculpture, in which the radial element is not markedly 

 feebler than the concentric and may be even stronger. Such species as T. 

 pretiosa Deshayes recall Conrad's Linearia, from which they differ in their 

 normal cardinals. 



Subgenus Arcopagia (Leach), 1827 (+ Cydippe Leach, 1852), 1827. Type 

 Tellina crassa Pennant. 



Shell large, solid, rounded, moderately convex, the flexure obsolete; pos- 

 terior left lateral absent, and the anterior obsolete, other teeth normal ; sinus 

 free, ascending obliquely; internal radii thick and strong but ill defined; 

 sculpture concentric, usually smoothish or not sharply lamellate, sometimes 

 reduced to incremental lines. Warm, temperate, and tropical seas. 



The chief feature of this group is the free sinus, but this in species other- 

 wise closely allied becomes more or less confluent. 



