PECTEN. 181 
a pointed granule where they cross the radial ribs; near the ventral border the ribs 
are often very closely placed. Ears triangular, with a few growth-lines; the 
anterior with granular ribs and nearly rectangular outer angle, the posterior smaller 
and with obtuse outer angle. 
Measurements : 
(1) (2) (3) (4) (5) (6) (7) (8) 
Length « 39 :; 38 . 33.5... 32 . 30 .. 28 . 26 |..20 mm. 
Height . 45 . 44 . 37 . 35 . 35 . 31 . 81 . 28 
(1—8) B. mucronata zone, near Norwich. 
39 
Affinities—In form, and in the possession of similar radial and concentric 
ornamentation, this species resembles some of the varieties of P. eretosus, but is 
easily distinguishable by the stronger radial ridges, ete. 
Remarks.—The differences in the appearance of the ornamentation in this 
species seem to depend mainly on the state of preservation; in some cases the 
right valve is almost smooth. Frequently in the larger specimens the later part of 
the valve is almost without ornament. By far the larger number of specimens 
which I have seen were obtained from the neighbourhood of Norwich, where 
it is a characteristic fossil. 
Type.—Vhe type of P. concentricus, Woodward, came from the Chalk of 
Norwich, but cannot now be found. ‘The types of P. Mautellianus, @Orbigny, 
came from the Senonian of Chavot (Marne). 
Distribution —M. cor-anguinum zone of South Croydon (Haling Pit). 
B. mucronata zone of Clarendon (near Salisbury), of Hartford Bridge and various 
other localities near Norwich. Upper Chalk of Sussex. 
Peormn (Cutamys) Ropinanpinus, @Orbigny, 1847. Plate XXXIV, figs. 7 a,b, 
8 a,b, 9 a,b, 10 a,h, hil 
12 a—c; Plate XXXV, 
fics, 1—TL0! 
co) 
1842. Pecoren wvrersrriatus, A. Leymeric. Mém. Soc. géol. de France, vol. vy, 
p- 10, pl. xiii, fig. 1 (non inter- 
striatus, Minster). 
1845. -— oBLiguus, EF. Forbes. Quart. Journ. Geol. Soe., vol. i, p. 249 (non 
obliquus, Sowerby ). 
1847. — Rosrnarpinus, A. d’Orbigny. Pal. Franc. Terr. Crét., vol. iii, 
p- 587, pl. cecexxxi, figs. 1—4. 
yo — intersrriatus, d’Orbigny. Tbid., p. 594, pl. eccexxniii, figs. 1—5. 
1850. —  apriensis, A. d’Orbigny. Prodr. de Pal., vol. ii, p. 119. 
