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The largest shell of this genus is Cucull&a crassatina; a ventricose shell, 

 of considerable thickness, three inches and a half in length, and four in 

 width ; the external surface smooth, except from fine transverse striae, 

 marking the growth of the shell, and faint traces of longitudinal sulci. 

 This shell is found in the neighbourhood of Beauvais, and is the only 

 species mentioned by M. Lamarck. 



Among the beautiful fossils yielded by the Devonshire whetstone-pits, 

 is a shell belonging to this genus, with specimens of which I have been 

 kindly favoured by Mr. Cleeve. This shell, which, if it has not been 

 already otherwise designated, may be named C. glabra, is a thick^ ob- 

 long, transverse shell, nearly smooth, being marked only by the fine 

 transverse striae formed by its growth. The beaks are separated by a 

 large flat rhomboidal area, with markings, which, when the valves are 

 united, assume a lozenge form. The line of the hinge is finely crenu- 

 lated, as well as the three transverse teeth, which terminate the hinge 

 at each end. Mr. Francis Crow, who, as has been mentioned, found, 

 in a field at Faversham, a silicious specimen of Strombus pes pelicani, ex- 

 actly agreeing with that which I had been favoured with from the 

 Devonshire whetstone-pits, found, in the same spot, several silicious shells 

 of this genus also. This coincidence deserves particular notice, since it 

 points out a singular agreement in the strata. The shell of this genus 

 found by Mr. Crow, though not unlike that of Devonshire in its general 

 form, is specifically different. This shell, if not already named, might 

 be designated as C. decussata. It is a thick oblong transverse shell, with 

 flattish longitudinal ridges, decussated "by fine transverse striae. The area, 

 separating the beaks, large, with slightly undulating markings in the 

 form of half a lozenge. The long line, as well as the transverse teeth 

 of the hinge, which in the preceding species were crenulated, appear, 

 in this, to have been smooth. Among the shells which I was favoured 

 with by Mr. Crow, is a single valve, which, from its extraordinary thick- 

 ness and great obliquity, I am disposed to consider as of different species 

 from either of the preceding : it is, however, in a state which will not 



