bilicus, crenulated or denticulated at its sides. One species of this genus 

 is found among the Hampshire fossils, Solarium canaliculatum, Lam. 

 Turbo, Brand. Foss. limit, p. 10, /. 7 and 8. This shell is distinguished 

 by its being marked, both on the upper and under surface, with trans- 

 verse granulated headings. The umbilicus large, funnel-shaped ; crenu- 

 lated and canaliculated on the internal edge of each turn. 



Lamarck describes nine species : S. patulum, S. sulcatum, S. canalicu- 

 latum, S. plicatum, S. spiratum, S. ammonites, S. patellatum, S. disjunctum, 

 S. bipons, 



XXXVIII. Turbo. A conoidal or slightly turreted shell, the opening 

 complete, rounded, and not toothed ; the margins always disjoined in 

 the upper part ; the columella smoothed at the base. 



It is from this latter circumstance, the end of the columella smoothly 

 blending with the right margin, and not forming a projecting tooth, that 

 this genus is separated from Monodonta. Some of the shells of this genus 

 very much resemble those of the genus Helix; but are to be distinguished 

 from them by the roundness of their opening not being broken, by the 

 projection into it of the last turn but one of the spire, which is the case 

 in the helices. Young specimens of cyclostoma may also be confounded 

 with turbines ; since, in their young state, they also have their margins 

 disjoined, like the turbines ; but, in their full-grown state, they become 

 circularly united, which the turbines never do. 



Lamarck gives four species of this genus : T. squamulosus, T. radiosm, 

 T. helicinoides, and T. denticulatus. The latter he has found fossil at 

 Grignon. 



XXXIX. Monodonta. An oval or conoidal shell, the opening entire, 

 roundish, with the two margins disunited : the truncated base of the 

 columella forming a tooth, projecting into the opening. 



This genus, of Lamarck, may be exemplified in Trochus labio, Linn. 

 This shell is not among the Paris fossils ; nor do I know of its exist- 

 ence among the fossil shells of this island : species of it are, however, to 

 be found in the cabinets of collectors. 



