74 



markable for its size ; the diameter of the base, and of the side of the 

 cone, each measuring above three inches. 



T. monilifer, Lam. T. nodulosus, Brand, is an elegant shell, and in the 

 French specimens has its markings exceedingly well preserved. T. sul- 

 catus, Lam. extremely like to T. granulatus, of Born. Tab. xn. Fig. 9 

 and 10, was obtained by Lamarck from the neighbourhood of Pontchar- 

 train, as well as from Grignon. I found one specimen of this shell among 

 the Harwich fossils, but which 1 have since broken. T. alligatus, Lam. 

 is distinguishable by six transverse ribs, some of which are cord-like, 

 and others crenulated. I have likewise found small specimens of this 

 shell in the Essex cliff. 



Among the Veronese fossils is one which has a singularity of appear- 

 ance, proceeding from a slight convexity in the sides of the cone. It is 

 formed of six whirls, on which are three rows of closely set, but distinct 

 beads; the base, which is circularly striated, possesses a considerable 

 degree of concavity. From this circumstance it has been named T. con- 

 cavus; but as this property is very common, I should prefer the name 

 T. convents, from the convexity of its sides. . 



Lamarck describes six fossil species of this genus : T. crenularis, T. mo- 

 nilifer, T. sulcatus, T. alligatus, T. ornatus, T. subcarinatus, T. bicarinatus, 

 T. agglutinans. 



Very large casts of this genus are found in different parts of Oxford- 

 shire, Gloucestershire, and Somersetshire ; those in the neighbourhood 

 of Bath being sometimes beautifully adorned with brilliant pyrites. 



XXXVII. Solarium. A depressed conical, nearly discoidal, umbili- 

 cated univalve shell : with the umbilicus crenulated or denticulated 

 at the margins of the windings. The opening approaching to qua- 

 drangular. 



The shells placed by Lamarck in this genus, were included by Lin- 

 nseus in the genus Trochus ; and are sometimes difficultly distinguished 

 from the shells of this genus, as well as from those of the genus Planorbis. 

 They are however, in general, plainly characterized by their large urn- 



