TRANSACTIONS OF WAGNER 

 72O 



TERTIARY FAUNA OK Kl.ORIDA 



Pecten (Pecten) biformis Conrad. 



1'cclcn liiftinnis Conrad, Proc. Acad. Nat. Sci. 1'liila., i., p. 306, 1843; Fos. Mod. Tcrt., 

 p. 73, pi. 42, %. I, 1845. 



Eocene (?) of the Pamunkey River, Virginia; Conrad. 



This rare and little-known species has the nepionic part smooth, or obso- 

 letely radially striated. There are five or six original ribs ; the succeeding 

 riblets are numerous, rough, irregular, and minutely imbricated ; the left valve 

 is concave, otherwise like the other. Alt. 26, lat. 25 mm. The type speci- 

 mens, which are all I have seen, have a somewhat abnormal aspect, and it 

 would not be surprising if the sudden change in the sculpture should prove 

 to be an exceptional feature. The horizon is also a little doubtful, and the 

 species may turn out to be Miocene when its true situs is identified. 



Pecten (Pecten) Burnsii n. s. 

 PLATE 34, FIGURE 8. 



Oligocene of the Chipola marls, Chipola River, Florida; Burns. 



Shell resembling P. Poulsoni Morton, but smaller, less inflated, and with 

 larger ears ; ribs fourteen, on the right valve strong, each divided by two 

 grooves so as to be tricarinate, the minor keels scabrous, the interspaces nar- 

 rower, with fine concentric sculpture ; ears and submargins radially threaded, 

 the ears large, subequal, the notch shallow ; left valve flat, the ribs angular, 

 simple, strong, with fine concentric sculpture ; ears large, radially finely 

 threaded; interior fluted. Alt. 18, lat. 19, diam. 6 mm. 



In specimens of P. Poulsoni of the size of this species the scabrous tri- 

 carination of the ribs has not yet appeared ; they are quite simple, and 

 number seventeen to twenty. This is probably one of those cases where a 

 lineal descendant takes on the adult character of the ancestor at an earlier 

 period in its life than the ancestor did, a character often indicating senility in 

 the life of the species. P. Burnsii appears to be rare, and the type disappears 

 entirely from the succeeding horizons, as far as known, being replaced in the 

 Miocene by large species such as P. hcinicydicus. 



Pecten (Pecten) Humphreysii Conrad. 



Pecten llitniplireysii Conr., Bull. Nat. Inst., ii., p. 94, pi. 2, fig. 2, 1842. 

 /'<//;/ lluinftlircysii var. Woolinaiii Heilprin, Proc. Acad. Nat. Sci. Phila., 1887, p. 405. 



Miocene of the Plum Point horizon, at Plum Point, Centreville, Burch, 

 and other localities in Maryland; older Miocene of Cumberland County, New 

 Jersey, at Shiloh and Jericho, and of Virginia and South Carolina. 



