194 CRETACEOUS LAMELLIBRANCHIA. 
PecTEN (AUQUIPECTEN) ARLESIENSIS, sp. nov. Plate XXXVII, figs. 9—11. 
Description.—Shell small, nearly circular, pointed dorsally, height and length 
nearly equal; nearly equilateral; convexity moderate. Apical angle about iOS 
Ears very unequal. 
Right valve with fifteen or sixteen strong, rounded, radial ribs, which are 
undivided, and of nearly equal size, but somewhat smaller anteriorly and poste- 
riorly. Ribs separated by strong, rounded grooves, a little narrower than the 
ribs. Fine, regularly-placed, concentric ridges cross both ribs and grooves, and 
are best marked near the umbo; on the ribs they develop into rather prominent, 
projecting scales. Near the posterior border of the valve the grooves are marked 
obliquely by closely set striz. Anterior ear very long, with a deep sinus, and two 
or three radial ribs bearing scales or tubercles. Posterior ear much shorter, the 
outer angle approximately rectangular. 
Left valve with similar ornamentation, but the ribs rather narrower and the 
scales somewhat more widely separated. 
Measurements : 
(1) (2 (3) (4) 
Length : 22 : 9-5 7 6 mm. 
Height : 23 : 975 i 6a 
(1, 3, 4) Totternhoe Stone, Arlesey. 
(2) Chalk Marl, Folkestone. 
Affinities —This species resembles the form referred by Geinitz (from the 
Turonian), and by Fritsch, to P. pulchellus, Nilsson (see p. 196), but it differs in 
having fewer and more widely separated ribs. These characters, as well as the 
scales on the ribs, also separate P. arlesiensis from P. campaniensis, d’Orbieny. 
T'ypes.—From the Chalk Marl of Folkestone. 
Distribution.—Chalk Marl of Folkestone, and from a deep boring in the axis of 
the Winchester anticline. Totternhoe Stone (H. subglobosus zone) of Arlesey. 
PECcTEN (ANQUIPECTEN) PULCHELLUS, Nilsson, 1827. Plate XXXVII, figs. 12a—e, 
Ss TAGs. lb: 
1827. Prctren putcHenuus, S. Nilsson. Petrific. Suecana, p. 22, pl. ix, fig. 12. 
— —  rneatus, Nilsson. Ibid., p. 22, pl. ix, fig. 13. 
1833. —  spurtus, A. Goldfuss. Petref. Germ., vol. ii, p. 51, pl. xei, fig. 10. 
_ —  PULCHELLUS, Goldfuss. Ibid., p. 51, pl. xci, fig. 9. 
