194 CRETACEOUS LAMELLIBRAXCHIA. 



Pecten (^quipecten) arlesiensis, sp. nov. Plate XXXVII, figs. 9 — 11. 



Description. — Shell small, nearly circular, pointed dorsallj, height and length 

 nearly equal ; nearly equilateral ; convexity moderate. Apical angle about 103°. 

 Ears very miequal. 



Right valve with fifteen or sixteen strong, rounded, radial ribs, which are 

 undivided, and of nearly equal size, but somcAvhat 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 striae. 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, l)ut the ribs rather narrower and the 

 scales somewhat more widely separated. 



Measurements : 



(1) 

 Length . 22 



Height . 28 . 



(1, .3, 4) Totterulioe Stone, Arlesey. 

 (2) Chalk Marl, Folkestone. 



Affinities. — This species resembles the form referred l)y Geinitz (from the 

 Turonian), and by Fritsch, to P. pulcheUns, Nilsson (see p. 19G), 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'Orbigny. 



Types. — 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. snhijlohosHs zone) of Arlesey. 



Pecten (^quipecten) pulchellus, Nilsson, 1827. Plate XXXVII, figs. 12 a— c, 



13, Ua,h, 15. 



1827. Pecten pulchellus, S. Nilsso7i. Petrific. Suecaua, p. 22, pi. ix, Hg. 12. 



— — LiNEATUS, Nilsson. Ibid., p. 22, pi. ix, fii,'. 13. 



1833. — spuEius, A. Goldfuss. Petref. Genu., vol. ii, \\ 51, pi. xci, fig. 10. 



— — PULCHELLUS, Gohy'uss. Ibid., p. 51, pi. xci, fig. 9. 



I 



(2) 



(3) 



(-1) 



9-5 



7 



G nun. 



9-5 



■>7 



G „ 



