Palaeo.ntographica Americana io 



"Shell elongated, aviculaeform, rostrated anteriorly, wintjed posteriorh', with a 

 prominent obtuse carination on the umbonal slope bounding the wing: rostrum decliv- 

 ous, marked off from the body of the shell by a broad hollow; basal margin of shell 

 sinuous, showing a median opening, and rapidly sloping upward in the direction of the 

 rostrum; posterior border deeply emarginate. 



Umbones acute, very eccentric, moderately elevated, and but slightly incurved, 

 with a gradual continuous slope to either extremity of shell ; hinge-line nearly the whole 

 length of shell, very narrow, pectinated with a crowded series of lamellar, transversely 

 directed teeth, which exhibit a tendency to become oblique and v-shaped on the pos- 

 terior half of the line; ligamental area broad, open, arching upward in a gentle curve, 

 longitudinally lined, and irregularly grooved by numerous diagonal or v-shaped furrows 

 resembling insect borings. 



Surface of shell ornamented with numerous radiating, wavy lines, alternating in 

 coarseness, which become more or less obsolete on the umbonal slope, and are wholly 

 wanting on both the beak and wing, which only show concentric lines of growth, of the 

 radiating lines on the anterior part of the shell the series runs about as follows: coarse 

 line, followed by two finer lines, then a slightly more prominent single line, again two 

 finer lines, and then a coarse line, same as first, marking the coarse lines at intervals of 

 about six or seven; interior of shell deep, cuneiform; margin entire. 



"Length, 5.4 inches; width across the beaks, 2.5 inches. 



"Caloosaliatchie, in the banks below Fort Thompson." — Heilprin, 1887. 



"This fine species is quite variable in the development of the extended wings which 

 suggested Professor Heilprin's name. In many specimens the posterior wing does not 

 exceed that usual in A. occidentalis, while in others it may extend an inch beyond the 

 rest of the shell. The anterior wing is less prominent and not a little more constant, but 

 is frequently paralleled by fossil and even by recent specimens of A. occidentalis Phil. 

 So far as yet known this species is confined to the Floridan Pliocene. The character of 

 the cardinal area is similar to that of A. noa:.'' — Dall. 



The anterior as well as posterior teeth may be v-shaped. The ribs are finer than 

 \v\.A. occidenfalis. 



Dimensions. — (Small valve). Ion. -1-16,-29; alt. -1-3,-13; semidiam. 8 mm. 



Occurrence. — Pliocene marls of the Caloosahatchie, Shell Creek, and Myaldca River. 

 —Dall. Pliocene of Shell Creek, Florida.— C. U. Museum. 



Area aquila Heilprin 

 Plate II, Figures i, 2 



Area aquila Heilprin, Wagner Free Inst. Sci., Trans., vol. i, p. 97, pi. 12, fii?. 31. 1887. 

 Area aquila Dall, Wagner Free Inst. Sci., Tran.s , vol. 3, pt, 4, p. 621, pi. 31, fig. 12, 1898. 



"Shell (known only by its left valve) elongated, rectangular, winged, profoundly 

 sulcated on the posterior slope; anterior border vertical, straight; basal line slightly 

 sinuous beyond the middle; hinge-line straight, of nearly equal length with the base; 

 teeth very numerous, gradually increa.sing in size toward either end, where they are 



