15 Q MOLLUSCA FROM THE CRAG. 



margin obtusely angulated ; spirally striated, with fine undulating striae ; rough and 

 imbricated beneath, aperture expanded ; umbilicus wide and open. 



Greatest diameter ; 1 line. 



Locality. Cor. Crag, Sutton. 



I have only two small specimens of this delicate and tender shell, which may 

 possibly be the young of some larger species ; it somewhat resembles &ig. Leachii 

 (Sowerby's Gen., fig. 3), Cryptostoma Leachii, Blain., but it appears to differ in several 

 particulars : the outer margin of the volution is more angulated, forming a flattish base, 

 which is rough and strongly imbricated by reflected lines of growth, and the umbilicus 

 is large, open, and visible up to the apex. 



MARSENIA, Leach t 1820. 



BULLA (spec.) Mont. 

 LAMELLABJA (spec.) Mont. 

 COKIOCELLA. De Blainville, 1824. 

 CHELINOTUS. Swains. 1840. 

 SIGARETUS Flem. Phil. Thorpe. 



Gen. Char. Shell internal, convolute, ear-shaped, thin, delicate, fragile, pellucid, 

 semipapyraceous ; consisting of a few rapidly increasing volutions, and an expanded 

 aperture, with a small depressed spire ; peritreme sharp and thin, confluent with the 

 columella, which is visible internally up to the spire ; shell wholly enveloped by the 

 mantle of the animal. 



In my Catalogue the above generic term was employed, in consequence of Dr. 

 Leach having given that name to the well-known British species, Sulla haliotoidea, 

 Mont., in his 'Mollusca,' a part of which was printed in 1820. A species of this 

 genus was described also by Montague (in the Linn. Trans., 1815, vol. ii, p. 186), 

 under the name of Lamellaria, and included with an animal of quite a different form, 

 which he had considered as its type, from which therefore it must be removed. In 1825 

 M. de Blainville (in his System of Malacology) proposed a genus under the name of 

 Coriocella ; but in his description of C. niyra, from the Isle of France, the animal he 

 considered as the type of his genus, he states that no trace whatever of a shell could 

 be discovered, "sans trace de coquille ext6rieur niinterieur" (p. 466). " Specimens of 

 Coriocella nigra in the British Museum, presented by Cuvier, and described by 

 De Blainville, have a distinct shell." (Vide Gray, Zool. Proc., 1847, p. 143.) 



As the name Marsenia was given to a determined species, and published with the 

 ulterior intention of characterizing such genus, it is I conceive the one that ought 

 to be adopted. 



