142 MOLLUSCA FROM THE CRAG. 



Shell transverse, ovate, inequilateral, thick, and strong ; ornamented with radiating 

 striae, decussated by concentric ridges ; a large elongated lunulc ; hinge with one 

 cardinal tooth and two lateral teeth in each valve : umbones prominent. 



Length, \ of an inch. Height, -j^ths of an inch. 



Locality. Cor. Crag, Sutton. 



This is by no means an abundant shell, and the above dimensions are to the 

 full amount of my largest specimen. 



It is a pretty species, covered externally with large obtuse rays, or depressed ribs, 

 they are but few in number in the young state, increasing as the shell enlarges by the 

 introduction of an intermediate ray, sometimes diverging in pairs ; they are crossed 

 I)y large obtuse ridges, or thickened lines of growth, placed sometimes in pairs, 

 generally more irregular ; the shell is nearly oval, but the anterior side is much the 

 larger of the two, the umbo is elevated, and immediately beneath it is one triangular, 

 sub-bitid tooth in the right valve, with two distinct, nearly equidistant lateral teeth, 

 and in the left valve are two, diverging on each side of the triangular space, for 

 the reception of the one of the right valve, with two lateral teeth : the rays are 

 visible w ithin the shell, and the muscle marks are not very deeply seated : the 

 anterior one is elongated, though not strictly of that ligulate or tongue-shaped 

 form so characteristic of the true Luciiiu. Tdlina reticulata, Poll. {Lucinu pecten, 

 Phil., 'En Moll. Sic.,' p. 31, T. 3, fig. 14), slightly resembles our shell, but it has finer 

 and more numerous rays, and is more orbicular. 



Some time since I sent over to M. Deshayes a few specimens of three or four 

 species, thought to bear a very close resemblance to those of the Paris basin, 

 requesting he would be kind enough to compare them with his own types ; and since 

 the first part of my MS. had gone to press, I have received a communication from that 

 gentleman, who has obligingly complied with my request. He says: "J'ai examine 

 avcc la plus grande attention vos trois espcccs Lucina squamosa, Erycina miliaria, and 

 Nucula miliaris, avec les types qui me restait dans ma collection ct il resulte pour moi 

 de cet examen repete un grand nombre de fois, qu'aucune de vos especes n'est 

 parfaitment identique avec celles di" notre bassin Parisien. Ces especes et les 

 notrcs ont entre elles de grandes resemblances mes elles offrent aussi des differences 

 constantcs." 



The means of determination possessed by M. Deshayes are probably sufficient 

 to enable him justly to separate the Crag shell from the Older Tertiary species, and 

 I have given a new name to our fossil upon such decision ; and in consequence of the 

 above opinion so strongly expressed, I have re-examined my own Crag specimens of 

 Nuciiiella miliaris with what I have considered as the same species from the Paris 

 basin in my own Cabinet, but with a high respect for the opinion of that able naturalist, 

 I cannot reconcile myself to the belief, that the differences observable between the two 

 are sufficiently prominent to justify a specific removal for the British fossil. 



