Yol. 52.] OF THE CHALK ROCK. 85 



III. Class GASTEROPODA. 



Order Prosobranchia. 



Pamily Fissurellidse, Risso. 



Genus Emakgin"ot,a, Lamarck, 1801. 



Emaeglntjla Sa^ct^e-Catharin^, Passy. 



1832. Emarginula Sanctce-Catliarince, A. Passy, ' Descr. Geol. de la Seine-In - 

 ferieure,' p. 335, pi. xvi. f. 1 ; 1843. A. d'Orbigny, ' Pal. Fran.?. Terr. CreV vol. ii. 

 p. 395, pi. ccxxxv. f. 4-6 ; 1877. J. S. Gardner, Quart. Journ. Geol. Soc. vol. xxxiii. 

 p. 198, pi. viii. f. 21, 22. 



1850. JEmarginula qffinis, J. de C. Sowerby, in F. Dixon's ' Geol. Sussex,' p. 348 

 <p. 383 of ed. 2), pi. xxvii. f. 20, 25 ; 1854. J. Morris, 'Cat. Brit. Foss.' ed. 2, p. 246 ; 

 1877. J. S. Gardner, Quart. Journ. Geol. Soc. vol. xxxiii. p. 200. 



Affinities. — This is a species with cancellated ornament produced 

 by longitudinal ribs of two sizes crossed by transverse ribs. It is 

 distinguished from E. unicostata, Gardner (Upper Chalk of Norwich), 

 by its more elevated form ; from E. loculata, de Ryckholt (Ceno- 

 manian of Tournay and Montignies-sur-Eoc), by possessing ribs of 

 two sizes ; and from E. Desori, Pictet and Campiche (Upper Gault 

 X)f Ste.-Croix), by having more numerous ribs. 



Remarks. — The specimens from the Chalk Rock agree in every 

 respect with Sowerby's E. affinis, and this, as suggested by 

 Mr. Gardner, is, I think, without doubt identical with E. Sanctce- 

 Caiharinoe. 



The figure given by Passy is very unsatisfactory, and is not 

 accompanied by a description of any kind, so that one is almost 

 obliged to rely on d'Orbigny's figures and diagnosis. The type 

 comes from the Cenomanian of Rouen. 



I have not been able to find Sowerby's type ; the specimen 

 figured by Gardner, which comes from the Chloritic Marl of White 

 JNore, is in the Museum of Practical Geology, No. -ffy. 



Localities. — England : Chloritic Marl of Wiltshire and Dorset ; 

 Lower Chalk of Kent and Sussex ; Chalk Rock of Cuckhamsley and 

 Xuton cutting. France : Cenomanian of Rouen. 



^EMARGrNULA aff. divisiensis, Gardner. 



1877. JE. divisiensis, J. S. Gardner, Quart. Journ. Geol. Soc. vol. xxxiii. p. 198, 

 jpl. viii. f. 19, 20. 



A cast from Cuckhamsley in the Montagu Smith collection is 

 allied to this species, but is hardly sufficiently well-preserved for 

 definite determination ; it is more ovate than E. divisiensis. The 

 type of E. divisiensis comes from the Upper Greensand of Devizes, 

 and is preserved in the British Museum. 



Emargintjla sp. 



A single specimen from the Chalk Rock of Cuckhamsley is 

 apparently new. It has a subcircular form, with a much elevated 

 and nearly central apex; it is in the form of a cast, and the 

 .ornamentation is unknown. 



