PLATE XX. 



Fig. 



^^ ^-■'hft.^^<1 flk*^*^^ ^•^'^ 



la, h, c. Ammonites rusticus ; from the Lower Chalk, near Lyme Regis ; in the Museum 

 of Practical Geology ; reduced to two thirds its natural diameter, p. 44. 

 The surface of the inner part has decayed away. 



la, side view. 



Id, back view. 



Ic, section of the outer whorl. 



T^w^j^f 2«, 6, and c. Ammonites Renevieri; from the Grey Chalk, near Blackdown, Isle of 



4 — Qc»->»vk,srct-cv?^ HvfoJt Wight; in the collection of E. Renevier, Esq., of Lausanne, p. 44. 



2a, side view. 

 26, front view. 

 2c, outline of a septum. 



3« and d. Ammonites Saxbii ; from the Grey Chalk of Ventnor, Isle of Wight ; in my 

 possession, p. 45 

 Sa, side view. 

 S6, front view. 



4a and d. Ammonites Vectensis ; from the Chloritic Marl of Ventnor, Isle of Wight ; in 

 my possession, p. 45. 

 4«, side view. 

 4:5, front view. 



