218 CRETACEOUS LAMELLIBRANCHIA. 
Mr. Clement Reid in the Chalk of Trimingham, probably belong to P. (Netthea) 
striatocostatus, Goldfuss. The six main ribs of the right valve are less prominent 
than in P. (N.) sevcostatus, 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.) sea- 
costutus, are found in the grooves and sometimes pass on to the ribs. On the left 
valve the ribs are im pairs. 
P. striatocostatus is found in the Senonian of Denmark, Aachen, Lemberg, ete. 
Genus—-VELOPECTEN, Philippi, 1898. 
(‘ Zeitschr. d. deutsch. geol. Gesellsch., vol. 1, p. 597.) 
VeELorectEN Stuperi (Pictet and Rouw), 1853. Plate XLI, fig. 11; Plate XLII, 
fies. _—4. 
1853. Huinnires Srupert, F. J. Pictet and W. Roux. Moll. Foss. Grés verts de 
Gentve, p. 504, pl. xlv, 
fig. 1. 
1866. — Saurert, H. G. Seeley. Ann. Mag. Nat. Hist., ser. 3, vol. xvii, 
p. 178. 
1870. — Scuvert, F. J. Pictet and G. Campiche. Foss. Terr. Crét. Ste. 
Croix (Mat¢ér. Pal. Suisse, ser. 5), 
pp. 232, 234, pl. clxxix. 
1875. -- = A. J. Jukes-Browne. Quart. Journ. 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 shehtly 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 
about fifteen primary ribs, which are narrow, strong, and slightly wavy, and are 
separated by broad, shallow interspaces; these ribs are prominent on the dorsal 
part 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 
