FREE INSTITUTE OF SCIENCE 



741 



TERTIARY FAUNA OF FLORIDA 



uniform. The ears are radially threaded, the byssal ear with four riblets over 

 a rather wide and deep notch. The submargins are short and small, with 

 traces of Camptonectes striation but no radial sculpture. The type is in the 

 Academy's collection. 



Pecten (Chlamys) decemnarius Conrad. 

 Pecten deceinnaritis Conr., Joiirn. Acad. Nat. Sci. Phila., vii., p. 151, 1834; Fos. Med. 



Tert., p. 49, pi. 24, fig. 2, 1840. 

 Pecten dispalatus Conr., Fos. Med. Tert., p. 74, pi. 42, fig. 3, 1845. 



Miocene of City Point, Coggins Point, and York River, Virginia, Burns 

 and Harris ; Pamunkey River, Virginia, Conrad ; also in the Ashley River 

 phosphate rock, of South Carolina, Dall. 



This species is notably irregular in its sculpture, the disk being sculptured 

 either by numerous more or less distinctly fasciculated, small, radial threads, 

 or the fasciculi may be replaced partially by stout, elevated, rounded ribs, with 

 wide, radially threaded interspaces. The radial sculpture may be nearly smooth 

 or covered with a conspicuous, dense, concentric lamellation. Three or four 

 of the ribs may be more prominent than the others, and the smaller ones 

 uneven in size and rugose, forming the variety dispalatus. When the fasciculi 

 are rib-like they are usually dichotomous. The umbonal region in typical 

 decevmariiis is usually feebly sculptured, but in the variety dispalatus the 

 ribbing approaches the beaks more nearly. The type of the latter has been 

 carefully compared, and the ears and surface agree exactly with those of the 

 decemnarius form. Large valves of the latter attain a height and width of sixty- 

 eight millimetres; the type of dispalatus measures twenty-four millimetres. 

 The cardinal crura are parallel with the hinge-line and moderately developed. 

 The byssal notch is wide and conspicuous, the posterior ears small. 



In sculpture this form almost exactly parallels the recent northwest 

 American P. hericais in its mutations. 



Pecten (Chlamys; ooccymelus n. s. 

 Plate 34, Figure i. 



Miocene of Plum Point, Maryland; Clark. 



Shell small, ovate, inflated, strongly sculptured, with unequal ears ; disk 

 with eighteen narrow, high, compressed ribs, with wider interspaces, which 

 near the basal margin carry one or two very small radial threads ; the backs 

 of the ribs support numerous high, evenly spaced, distally guttered, small 

 spines ; in the interspaces only transverse sculpture of wavy incremental lines ; 



