TRANSACTIONS OF WAGNER 

 862 



TERTIARY FAUNA OF FLORIDA 



Miocene of the York River, Virginia, Harris ; and of the Natural Well, 

 Duplin County, North Carolina ; Pliocene of South Carolina, on the Wacca- 

 maw River; Pleistocene of South Carolina, and living, in from twelve to thirty 

 fathoms, from the vicinity of Beaufort, North Carolina (Stimpson), southward 

 to Florida ; Uall and Rush. 



The recent shell does not appear to differ in any respect from the Miocene 

 fossil. Stimpson was of the opinion that Mya simplex Holmes (P. -PI. Fos. S. 

 Car., p. 55, pi. 8, fig. 16, 1858), from the Pleistocene of Simmons Bluff, South 

 Carolina, is identical with Parainya, but Holmes's species has a narrow chon- 

 drophore, much as in Splicnia, but smaller, with a prominent tooth in front of 

 it, and, as far as one can judge from the shell alone, belongs in the vicinity of 

 Basterotia, probably in the subgenus Fiilcrella. 



Superfamily MACTRACEA. 



With the exception of Neumayr's and Bittncr's investigations, the Mac- 

 troid hinge appears to have been studied without reference to large series of 

 specimens of a single species, and with little consideration of evolutionary 

 progress or dynamic modification.* In order to discuss it properly it is 

 necessary to pay much more minute attention to its details and the relations 

 of its parts than has hitherto been thought required. 



To make these details clear and avoid excessive verbiage, it becomes 

 necessary to name the parts of the hinge, and for clearness I prefer to use, for 

 the most part, plain English terms, applied for the occasion in a particular and 

 exclusive sense. The memory is thus not burdened with the task of learning 

 a wholjy new vocabulary, and can devote its energy solely to following the 

 description. 



The essential parts of a true Mactroid hinge are as follows : In the left 

 valve, an anterior and posterior lateral lamina, and a bifid or A-shaped car- 

 dinal tooth in front of a pit for the resilium ; above the latter a scar or surface 

 of insertion for the ligament. In the right valve, two anterior and two pos- 

 terior laminae, between which the laterals of the opposite valve are received ; 

 two lamellar cardinal teeth, inclined to each other at an angle above and 

 usually more or less solidly united at this line of junction, below which the 

 cardinal of the opposite valve fits ; behind them the chondrophore, and above 



*The excellent studies of Bernard, Bull. Soc. Geol. de France, 3me Ser., t. xxiii., pp. 141-144, 

 1895, appeared after the preparation of this part of my manuscript. W. II. U. 



