90 palbo^tolocvx cw ^y^n t ;ra^m. 



shorter and not quite so attenuate, while the umbos are larger and more 

 rounded and prominent. The anterior end of the shell is so little gaping 

 that it can hardly be said to be a feature, at least when examining the sep- 

 arated valves it is scarcely apparent; but the posterior side is very distinctly 

 so. The greatest difference which I have noticed between Mr. Wagner's 

 description and the features of the New Jersey shells lies in the great promi- 

 nence of the teeth in the latter, whereas he says they are not prominent in 

 his specimen. Still I do not think this of much importance, but only prob- 

 ably an individual difference. The resemblance to P. reflexa Say is too 

 slight to need comparison here. The other nearest approach to this one is 

 seen in P.porrecta Conrad (Miocene Fossils, p. 71, PI. xli, fig. 2), but here the 

 posterior end is still more elongate and narrowed, and the teeth more slender 

 and smaller. Still I think it probable they may be only variations of the one 

 species. In the interior of this shell the siAus is very large and much deeper 

 than in P. reflexa or P. Americana, but the line is not broken into dots or 

 patches, as is required in the genus Grlycimeris of Klein, consequently I 

 retain it under Panopaea. 



Formation and locality: In the gray marly beds of the Miocene at Jericho, 

 N. J. From the collection of the National Museum. 



Genus SAXICAYA Bellevue. 



SAXIOAVA MYCEFORMIS. 



Plate xvi, figs. 4 and 5. 



Saxicava myceformis Conrad: Proc. Acad. Nat. Sci. Phila., 1862, p. 585; Meek, Check 



List Miocene Foss., p. 12. 

 Thraeia myceformis Conrad: Am. Jour. Conch., vol. 2, p. 70, PI. IV, fig. 3. 

 Thraeia myceformis Heilprin: Tert. Geol. U. S., p. 8; Miocene Mollusca of New Jersey, 



Proc. Acad. Nat. Sci. Phila., 1887, pp. 397 and 403. 



" Ovate, thin and fragile, inequilateral; extremities rounded; surface 

 marked with fine rugose concentric lines; cardinal teeth small, two in the 

 right valve." (Conrad in Proc. Acad. Nat. Sci., Phila., 1862, p. 585.) In 

 the American Journal of Conchology, loc. cit., Mr. Conrad describes the 

 same shell as follows: " Ovate, inequilateral; posterior side somewhat pro- 



