TURRILITES. 



TESTA univalvis, libera, spiralis, turrita, conca- 

 merata, spira sinistrorsa, gradatim acuminata, 

 septis siphunculo perlbrato, marginibus sinuo- 

 sissimis. 



Thk only circumstance in which this Genus diflFers from 

 Ammonites is its turrited form, the latter being spiral but 

 having its volutions all increasing upon the same plane. 

 There appear to us to exist, all in a fossil state only, five 

 genera of shells with chambers whose septa are sinuous 

 at their edges, namely, Baculites, Hamites, Turrilites, 

 Ammonites and Scaphites, which are well distinguished by 

 the form peculiar to each ; but we think it unnecessary 

 for the purposes of science to adopt genera such as La- 

 marck's Ammonoceras, founded upon a slight variation 

 from perfect contiguity in the volutions : if we could 

 adopt such a Genus we might for the same reasons raise 

 almost every species to the rank of a Genus. Nautellip- 

 sites and Ammonellipsites appear to iis to be founded on no 

 better characters, indeed we are convinced that the ellip- 

 tical form of both is only caused by compression in one par- 

 ticular direction, operating at the time of their imprison- 

 ment. 



Shell univalve, free, spiral, turrited, chambered, spire 

 sinistrorsal, gradually acuminated, septa perforated by a 

 siphunculus, their margins much sinuated. 



The shells of this Genus being only found in a fossil 

 state, nothing is of course known of its animal, nor of 

 the form of its aperture ; it appears to have lived only at 

 one particular period, as the fossil remains only occur in 



