218 CRETACEOUS LAMELLIBRANCHIA. 



Mr. Clement Reid in the Chalk of Trimingham, probably belong to P. (Neithea) 

 striatocostatus, Goldfuss. The six main ribs of the right valve are less prominent 

 than in P. (A.) sexcostatus, and both these and the ribs in the interspaces bear two 

 or three small, almost linear ribs, so that the total number of ribs on the valve 

 becomes considerable ; fine concentric ridges, similar to those of P. (N.) sex- 

 costatus, are found in the grooves and sometimes pass on to the ribs. On the left 

 valve the ribs are in pairs. 



P. striatocostatus is found in the Senonian of Denmark, Aachen, Lemberg, etc. 



Genus — Velopecten, Philvppi, 1898. 



(' Zeitsclir. d. deutsch. geol. Gesellscli., vol. 1, p. 597.) 



Velopecten Stuukiu (Pictet and Boux), 1S53. Plate XLI, fig. 11; Plate XLII, 



figs. 1 — 4. 



1853. Hinnites Studert, F. J. Pictet and W. Boux. Moll. Foss. Gres verts de 



Geneve, p. 504, pi. xlv, 

 fig. 1. 

 1866. — Salteri, H. G. Seeleij. Ann. Mag. Nat, Hist., ser. 3, vol. xvii, 



p. 178. 

 1870. — Studeri, F. J. Pictet and G. Camjnche. Foss. Terr. Cret. Ste. 



Croix (Mater. Pal. Suisse, ser. 5), 

 pp. 232, 234, pi. clxxix. 

 1875. A. J.Jukes-BraH-ne. Quart. Jouru. Geol. Soc, vol. xxxi, 



p. 296. 



Description. — Shell large, oval or nearly circular, somewhat inequilateral and 

 irregular; height a little greater than length. Hinge-line long, sometimes almost 

 equal to the length of the shell. Ears very unequal ; the anterior left ear not dis- 

 tinctly separated from the rest of the valve. 



Right valve flat, sometimes slightly concave, with more or less undulating 

 surface. Radial ribs much more numerous, smaller, and closer together than on 

 the left valve, alternately larger and smaller. Numerous growth-ridges cross the 

 ribs, and produce a serrate appearance. Byssal sinus very deep; anterior ear very 

 large. 



Left valve convex, with a more or less undulating surface, ornamented with 

 ;i liDi it fifteen primary ribs, which are narrow, strong, and slightly wavy, and are 

 separated by broad, shallow interspaces; these ribs are prominent on the dorsal 

 par! of the valve, but become smaller on the ventral part, especially in large speci- 

 mens. A secondary rib is usually introduced in the middle of each interspace, at 

 varying distances from the umbo; and between this and the primary ribs on each 



