TRANSACTIONS OF WAGNER 



596 



TERTIARY FAUNA OF FLORIDA 



Y. montcrcyensis Dall, otherwise very close to Y. tliracicEforniis, does not gape 

 perceptibly more than Y. glacialis. The soft parts of Y. thrackefonins differ 

 in no essential respect from those of Portlandia glacialis. I cannot regard 

 the differences of any of the above forms as of more than sectional value. 

 They all intergrade in a large series of species. 



Yoldia laevis Say. 

 Nucula Iccvis Say, Journ. Acad. Nat. Sci. Phila., ist Ser. , iv., p. 141, pi. x., fig. 5, 1824. 



Miocene of Maryland (Say); St. Mary's County, Maryland; York River, 

 Virginia; Warwick and Dismal Swamps, Virginia; Burns, Harris, Haldeman, 

 etc. 



This species is probably the ancestor of the Pleistocene and recent 

 Y. limahila Say. It differs from the latter by its proportionally larger chon- 

 drophores, smaller and more numerous teeth, somewhat more pointed pos- 

 terior end, and less compressed escutcheon. A very large series compared 

 shows these differences to be constant. 



Yoldia psammotgea n. s. 

 Plate 34, Figure 20. 



Claiborne sands, at Claiborne, Alabama ; Burns. 



Shell smooth, or with faint incremental lines, inequilateral with low 

 beaks, the dorsal and ventral margins subparallel ; valves elongated, rounded 

 in front and behind, the posterior part somewhat compressed and attenuated ; 

 anterior end with a moderate gape; lunule and escutcheon elongated, very 

 narrow, almost linear. Lon. 21, alt. 9, diam. 6 mm. 



This species is represented by two specimens withthe valves closed and 

 filled with a rather hard matrix, so that the hinge characters are inaccessible. 

 It is clearly distinct from any of the described species of the American 

 Eocene, and peculiar in its elongated solenoid form. It cannot be confounded 

 with Y. claiboriioisis Conrad, from the same horizon. It would find a place in 

 the section Orthoyoldia Verrill. 



Yoldia frater n. s. 

 Plate 32, Figure i. 



Oligocene of the Chipola beds in Calhoun and Walton Counties, Florida, 

 Dall, Burns, and Johnson; also in the Alum Bluff sands at Oak Grove, Santa 

 Rosa County, Florida, Burns. 



Shell polished, thin, elongate, much resembling Y. lavis, from which it is 



