174 CRETACEOUS LAMELLIBRANCHTA. 



figured as P. chmgafus by d'Orliigny appears to belong to anotlier species. P. 

 ohlir/nvs, SoAverljy, is probably identical with P. elongatus ; the type, however, is 

 missing, and the figures do not show the character of the ornamentation satis- 

 factorily, but it is clear from the description that the ribs were in triplets and 

 covered with numerous scales. 



This is a moderately common species in the U]:)per Greensand and Lower 

 Chalk. In a specimen from the Chalk Marl of Ventnor (PL XXXI, fig. 12) 

 the shell is proportionately higher, and has a smnller apical angle than usual ; 

 it is near to the form figured by Geinitz (1872, pi. xliv, figs. 2, 3). Other 

 specimens connect this high form with those of normal proportions. A few 

 specimens from the Lower Greensand of Upware — now in the Woodwardian 

 Museum, and in Mr. J. F. Walker's collection, were referred by W. Keeping to 

 P. Baulinianus ; their state of preservation is less satisfactory than that of Upper 

 Cretaceous examples, but they approach closely some forms of P. elongatus from 

 the Upper Greensand and Chalk, and nre probably correctly referred to that 

 species. 



Types. — The type of P. ehmgatns came from the Cenomanian of Le Mans. 

 The type of P. oUiquus from the Upper Greensand (? Devizes) cannot l)o found in 

 the Sowerby collection. The types of P. Rauliniauus came from the Albian of Grand 

 Pre and Macheromenil (Meuse). 



Distribution.— Ganlt of Folkestone (zones viii and xi of Price). Cambridge 

 Greensand. Upper Greensand of Ventnor. Malmstone of Alton. Chloritic Marl 

 of Maiden Bradley. Rye Hill Sand of Warminster. Chalk Marl of Ventnor, 

 Folkestone, and Burwell. Totternhoe Stone (ff. suhgJohosus zone) of Arlesey and 

 Burwell. Lower Greensand of Upware (see " Remarks" above). 



Peoten (Chlamys) ciiETOSUs, Defrance, 1822. Plate XXXII, figs. 4 a — a, b a,h, 



6 a—c ; Plate XXXIII. 



1822. Pecten cbetosus, Defrance. A. Brongniart. Descript. gool. Envir. de 



Paris (in Cuvier's Ossein, foss., vol. ii), 

 pp. 2.51, 598, pi. iii, fig. 7. 



— — ARACHNOiDES, Defronce. Brongniart. Ibid., pp. 251, 599, pi. iii, 



fig. 8. 



— — NiTiDA, O. Mantell. Foss. S. Downs, p. 202, pi. -xxvi, figs. 4, 9 



(?fig. 1). 



1823. — NiTiDus, J. de C. Sowcrhy. Miii. Conch., vol. iv, p. 130, pi. cccxciv, 



fig. 1. 

 1825. — CRETOsus, Defrance. Diet. Sci. uat., vol. xxxviii, p. 207. 



— — AKACHNoiDK.s, Dcfrancc. Ibid., j). 2tiG. 



