FREE INSTITUTE OF SCIENCE 



809 



TERTIARY FAUNA OF FLORIDA 



about oyster beds, from Maryland to Florida, Nicaragua (Richmond), New 

 Grenada (Totten), St. Thomas (Dunker), and Vieque, West Indies. 



A review of the American Congerias in the National Museum shows 

 that besides the above-mentioned species there is found in the United States 

 the C. Rossmflss/cri Dunker (1858, Rve., fig. 45, + C. Sallei Reeve, fig. 44, 

 1858, not of Reclux, 1852), which occurs near Tampa, Florida, and is said to 

 extend to Brazil. It is distinguishable from the common Icitcoplucata by its 

 more triangular, anteriorly flattened, heavier shell. The C. Gimdlac/ii Dunker 

 (1858), which has a more conspicuous myophore, is found in Cuba, while the 

 C. coclilcata is common at Colon, on the Isthmus of Darien. There may be 

 one or two more identifiable forms in the West Indies, but the shell is variable, 

 passing through about such a set of mutations as does Mytilus eiinlis, and too 

 much stress should not be laid on slight differences. None of the other 

 species mentioned has yet been found fossil, but a species is not uncommon 

 in the Florida Pliocene which is obviously different from any of them. It 

 is notable that the European type, Dreissciisia, does not occur in Africa or 

 America, though it is represented by a species (D. Massiei L. Morlet) in 

 Cochin China. In Africa, America, China, and the Viti Islands Congeria is 

 present. 



Congeria lamellata n. s. 

 PLATE 35, FIGURES 13, 14, 15. 



Pliocene marls of the Caloosahatchie and Shell Creek, Monroe County, 

 Florida ; Ball and Willcox. 



Shell subtrigonal, externally smooth, except for concentric undulations 

 due to irregularities of growth ; anterior side flattened below the beaks, the 

 periphery of the flattened area rounding over towards the disk ; beaks subacute 

 and slightly twisted outward, byssal gape very narrow ; dorsal slope sub- 

 arcuate with no pronounced angle at the distal end of the hinge-line, in the 

 vicinity of which the valves arc somewhat compressed ; internal margins 

 smooth ; cardinal border with a wide groove for the reception of the ligament, 

 this groove being continuous to the beaks ; septum small, separated from the 

 groove by a A-shaped lamella which on the anterior side is conspicuously 

 produced and extends along the anterior margin about twice the length of 

 the septum beyond the septum ; myophore small, entirely hidden below the 

 septum and formed by a callous eminence bearing the scar of the retractor 

 muscle of the foot upon which the strain from the byssus comes; adductor 



