606 PROCEEDINGS OF THE NATIONAL MUSEUM. vor,. r.t. 



lets, which become higher and more broadly undulated to about the 

 first third of the disk and then flatten out and become nearly obscure 

 near the margin ; whole surface with fine irregular growth lines, not 

 sufficiently prominent to destroy the somewhat smooth appearance 

 of the surface ; posterior dorsal area depressed, nearly smooth and not 

 sharply defined; lunule lanceolate, defined by a faint ridge, and is 

 more distinct and depressed than posterior area. Anterior and pos- 

 terior and basal inner margins crenulated with alternate ridges and 

 pitted grooves. Anterior and posterior adductor scars prominent. 

 Middle right cardinal tooth is large, slightly furrowed, elevated, and 

 has crenulated inner sides. The anterior right cardinal is small, 

 slightly elongate and lower than middle, but higher than posterior. 

 Posterior terminal cardinal narrow and elongate. The lateral tooth 

 and laminae not prominent and extend to about two-fifths length of 

 valve. 



Type (Cat. No. 166914 U.S.N.M.).— This measures— right valve, 

 length, 9.5 mm.; height, 9.3 mm.; diameter (double), 5.2 mm. 

 This species is closely related to Astarte (distans var. ?) fioridana 

 Dall, but differs in the following respects: It is smaller; has less 

 pointed and anteriorly inclined beaks ; has shorter and more rounded 

 posterior basal end; has more indistinct lunule and escutcheon 

 areas; has shorter ligamental depression; and has more rounded 

 undidations and smoother surface. The young forms of both Astarte 

 {distans var. ?) floridana Dall and Astarte distans Conrad are much 

 more depressed, thinner, more wrinkled, longer and more rostrate 

 than the present species. In no specimen of these species examined 

 was any of equal size found that possessed the crenulated inner mar- 

 gins which all unworn specimens of the nev/ species show. Astarte 

 glenni Dall lacks the undulated surface, has a more drawn out beak 

 and a stronger hinge. 



Type-locality. — Miocene of Florida, E. -Gomillion's field, one- 

 fourth mile east of Redbay, Walton County, Florida. C. Wythe 

 Cooke, collector. 



DIPLODONTA WALTONENSIS, new species. 



Plate 113. fig. 7. 

 Shell medium size, ovate-trigonal, moderately convex, very thin, 

 marked by many fine, closely spaced, inconspicuous, concentric 

 rounded tlireads, which are neiU'ly obscure on upper part of the disk, 

 but visible near the margin. Anterior side shorter than the posterior, 

 with the margin well rounded. Upper posterior part of disk rounded 

 and somewhat truncated near the margin, the anterior side sloping 

 more gradually. Beaks are low and smaU. Hinge plate narrow and 

 channelled in front; cardinal teeth normal; the left anterior cardinal 

 being short and distaUy sulcated, while the posterior is long. 



