TRANSACTIONS OF WAGNER 

 1386 



TERTIARY FAUNA OF FLORIDA 



Shell ovate-quadrate, solid, inequilateral, with small, pointed, inconspicu- 

 ous beaks situated at about the posterior third ; dorsal areas narrow, elongate, 

 the posterior with one obsolete radial rib about the middle of it, the anterior 

 without radial sculpture ; disk with seven to nine flat radial ribs with some- 

 what narrower interspaces, which are shallow ; the ribs become obsolete dis- 

 tally, sometimes as early as the middle of the adult disk ; concentric sculpture 

 of subequal low threads, with nearly equal interspaces, which do not become 

 lamellose on the dorsal areas and cover the whole shell ; lunule larger in the 

 left valve, moderately impressed, cordate ; escutcheon linear or obsolete ; hinge 

 normal, strong ; inner margins very finely crenulate. Alt. 7.5, Ion. 7.5, diam. 

 5.0 mm. 



The above dimensions are above the average and taken from the largest 

 specimen. The number of ribs is very commonly only seven. 



This species has less prominent sculpture than the later ones and shows no 

 leaflike lamellation or spinosity on the posterior dorsal area. 



Phacoides (Bellucina) waccamawensis n. sp. 



PLATE 52, FIGURE 2. 



Lucina costata Dall, Trans. Wagner Inst., iii., p. 210, 1892 ; not of Tuomey and Holmes, 

 1855, or of Holmes, 1860. 



Pliocene of the Waccamaw district, at Tilly's Lake, South Carolina, John- 

 son ; and of the marls of the Caloosahatchie and Shell Creek, Florida, Dall 

 and Burns. 



Shell resembling P. Tuomeyi but smaller, more convex, with nine or ten 

 radial ribs which are stronger and with deeper interspaces and which are very 

 little feebler distally ; the concentric sculpture is coarser and more prominent, 

 and on the posterior rib and the medial ridge of the posterior dorsal area is 

 raised into small leaflets or spines in perfect specimens. Near the base there 

 frequently are small radial stride between the ribs, and the lunule is much more 

 conspicuous in the left valve. The hinge and crenulations much as in the last 

 species. The largest valve found measured : Alt. 7, Ion. 7, diam. (double) 

 6 mm. 



This, the Pliocene form, is readily distinguished from P. Tuomeyi of the 

 upper Miocene, though the general plan of ornamentation is the same. 



Phacoides (Bellucina) amiantus Dall. 

 Lucina costata Holmes, P.-P1. Fos. S. Car., p. 28, pi. vi., fig. 2, 1860 ; not of Tuomey and 



Holmes, 1855. 

 Phacoides (Bellucina) amiantus Dall, Synopsis Lucinacea, p. 826, pi. xxxix., fig. 10, 1901. 



