MIOCENE MOLLUSC A AND .CKUSTAOEA. 49 



(ienus AXIN^A Poli. 



AXINEA LENTIFORMIS f. 



Plate vii, figs. 5 and 6. 



Pectunculus lentiformis Conrad: Foss. Shells. Tert. formations U. S., p. 36; Miocene 

 Foss., p. 64, PI. xxxvi, fig. 1; Tuomey & Holmes, Pliocene Foss. S. C, p. 48, 



PI. xvn, fig. 2 ; Emmons, Geol. N. Car., p. 286; Heilprin, Acad. Nat. Sci. Phil., 

 1887, p. 402. 



Axinea lentiformis Conrad: Proc. Acad. Nat. Sci., Phil., 1862, p. 580; Meek, Check 

 List, p. 5. 



Conrad gives a description of this species in his Fossils of the Median 

 Tertiary, p. 64, as follows: "Lentiform, thick and ponderous, with fine, 

 closely arranged, radiating lines, and distant more profound lines, giving the 

 shell a slightly ribbed aspect; valves widest above or across the base of the 

 umbones, where the margins are rather obtusely rounded; umbo lar^e, and 

 the summit prominent; dorsal margins oblique, curved; cardinal plate 

 dilated, the teeth very large and oblique; marginal crense rather narrow 

 and approximate." 



The specimens of Axine& which h^ve come to me from the New Jersey 

 beds are all small, young individuals; the largest being scarcely more 

 than five-eighths of an inch in width — so small in fact that they scarcely 

 show the true specific features, and I am. somewhat in doubt as to which of 

 these species to refer them, A. lentiformis, A. parilis, or A. passa. The 

 shells are more circular in outline than any of the three except A. parilis, 

 while the teeth more nearly resemble those of A. lentiformis than of either 

 of the others, being proportionally large and very distinct, while the inner 

 extremities are very slightly inclined. In A. parilis and in A. passa, the 

 teeth are shorter than in the other, and are each more distinctly bent when 

 the shells are fully grown; but in young specimens from Yorktown it is 

 nearly impossible to distinguish the specific features. The surface of the 

 New Jersey specimens more closely resembles that of A. parilis than of 

 any of the others, as the ribs are flat, with a simply impressed line dividing 

 them, with about five longitudinal striae on each; while in the other species 

 they are usually more rounded and prominent, Taking all these features 



MON XXIV 4 



