170 CRETACEOUS LAMELLIBRANCHIA. 



Left valve a little more convex, with similar ornamentation ; ears slightly 

 unequal. 



Measurements : ' 



U) (2) (3) 



Length . 37 . 34 . 24 mm. 



Height . 49 . 43 . 31 „ 



(1) Greensand, Haldon. 

 (2, 3) Chalk Marl (Bed 11), Dunscombe. 



Affimties. — P. acummatus, Geinitz,^ resembles closely this species, but seems to 

 differ from it in having few or no scaly spines on the ribs, and also in having the 

 concentric ornament somewhat coarser ; the ribs, as a rule, are also less sharp and 

 somewhat less numerous. The state of preservation of the spines in P. suhactdus 

 varies a good deal in difFerent specimens ; in some cases (as in fig. 8) they are 

 absent from the greater part of the surface. It seems probable, therefore, that the 

 comparison of good series of specimens might show P. aciiminatiis and P. suhacutus 

 to be identical. 



The form from the Cambridge Grreensand, referred to this species by Jukes- 

 Browne, possesses the characteristic concentric ornamentation, but has rather more 

 numerous ribs ; only three specimens have been seen, and since they are rather 

 imperfectly preserved, the determination of the species cannot be regarded as quite 

 certain. 



Type. — From the Cenomanian of Le Mans. 



Distribution. — Cenomanian :^Bed 10 of Hooken, Beds 11 and 12 of Dunscombe, 

 Bed 12 of Branscombe. Greensand of Haldon. ? Cambridg'e Greensand. 



Pecten (Chlamys) elongatus, Lamarck, 1819. Plate XXXI, figs. 10, 11 a,h, 12 a,h, 



13; Plate XXXII, figs. la,b, 



2a,h, 3a,h. 



1819. Pectkn elongatus, Lamarck. Anim. saus Vert., vol. vi, ]>. 181. 

 1822. — OBLiQuus, /. de C. Sowerhy. Mia. Couch., vol. iv, i^. 95, pi. ccclxx, 



fig. 2. 



1 Geinitz, ' Char. d. Schicht. u. Petref. des siit-hs-bbhin. Kreidegeb.,' pt. 3 (1842), p, 84, pi. xxi, 

 fig. 6; Reuss, 'Die Verstein. der bohm. Kreidefonnat.,' pt. 2 (1846), p. 29, pi. xxxix, figs. 20, 21; 

 d'Archiac, ' Meiri. Soc. gt'ol. de France,' ser. 2, vol. ii (1847), p. 309, pi. xvi, fig. 3 ; Kunth, ' Zeitschr. 

 d. deutsch. geol. Gesellsch.,' vol. xv (1863), p. 725 ; Michael, ibid., vol. xlv (1895), p. 235 ; E(3nier, 

 ' Geol. V. Oberschles.' (1870), p. 333, pi. xxvi, fig. 3 ; Geiuitz, " Das Elbthalgeb. in Sachsen " (' Palffiouto- 

 graphica,' vol. xx, pt. i, 1872), p. 194, pi. xliii, fig. 16; pi. xliv, fig. 1 ; Fritsch, ' Bohni. Kreidefonnat. 

 III. Iserschicht.' (,1883), p. 116, fig. 89; Notling, "Die Faiuia d. balliscli. Ciuoniau." (' Palaeout. 

 Abhaudl.,' vol. ii, 1885), p. 19, pi. iii, fig. 2; Leonhard, " Die Kreideforniiit. iu Oberschles." (' Palaeonto- 

 graphica,' vol xliv, 1897), ]). 26. 



