Vol. 52.] A DELIMITATION OP THE CENOMANIAN. 149 



it is only necessary to look at plate v. of his Monograph, where 

 both shells are figured, to see how nearly they approach one another 

 through the least lamellose variety of T. squamosa (fig. 11). 



Davidson says that T. squamosa is very common in the ' Craie 

 chloritee of Kouen ' : it may be so, but in the middle of the 4 Craie 

 glauconieuse of St. Jouin ' we find a form which is quite destitute 

 of squamose ridges, and is ornamented with nearly straight but, 

 slightly undulating, capilliform striae. Except that it is of small 

 size, it agrees more closely with d'Archiac's figures of T. capillata 

 (Mem. Soc. geol. Fr. ser. 2, vol. ii.) than with the T. capillata of the 

 Red Chalk figured by Davidson. 



In this connexion we would recall the fact that T. capillata 

 has been found by one of us in the Totternhoe Stone or • Grey Bed' 

 of Lincolnshire, and consequently well up in the Lower Chalk (see 

 Quart. Journ. Geol. Soc. vol. xliv. p. 349). It has therefore a wider 

 distribution in beds of Cenomanian age than in those of earlier 

 epochs, and we are inclined to think that the Lower Greensand form 

 figured by Davidson may have to be separated from it. 



Lamellibrancliiata. 



OSTEEA CANALICULATA, SoW. = 0. LATEKALIS, NilsS. 



This is the Chama canaliculata of the ' Min. Conch.' vol. i. pi. 26. 

 fig. 1 (1812), not the Ostrea canaliculata of a later volume (pi. 135. 

 fig. 1). 



The Chama canaliculata of Sowerby is the Ostrea lateralis of 

 Nilsson (1827), as pointed out by d'Orbigny ; and, having compared 

 many French and English specimens, we agree in regarding them 

 as the same shell, but Sowerby's name has the priority. 



The shell which Sowerby called Ostrea canaliculata cannot bear 

 that name, and, as it seems to be identical with the 0. lunata of 

 Nilsson, it should be so designated. 



0. canaliculata (Sow., sp.) is a characteristic Cenomanian shell, 

 and 0. lunata belongs to the highest White Chalk of Trimingham 

 and Mundesley. 



Pecten intekstkiatus, Leym. 



This name has frequently appeared in lists of Cretaceous fossils, 

 and has been applied indiscriminately to Lower and Upper Creta- 

 ceous species. Leymerie, in 1842, gave the name to an Aptien 

 species which is figured by d'Orbigny under that name in the 'Pal. Fr. 

 Terr. Cret.' pi. 433. figs. 1-5, but in his ' Prodrome' (vol.ii. p. 169) 

 he changed the name to ajytiensis, hecsiuse he found that interstriatus 

 had been used for another species by Minister in 1841. The latter 

 name, therefore, should not be used for any of the Cretaceous Pectens. 

 The Lower Greensand species (P. aptiensis) has its own distinctive 

 characters and does not range into Gault or Upper Greensand 

 though it doubtless was the ancestor of the later interstriate Pectens, 



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