( 35 ) 



DIVISION XVII. GONYOSTOMATA 



I. Trochus. (1) Lam. 



Conical ; mouth more or 

 less quadrangular, in an 

 oblique plane to the axis 

 of the shell ; operculum 

 thin, horny, orbicular. 



GENERA. 

 Base flat or concave. 



Marine, or inhabiting 

 the brackish ponts com- 

 municating with the sea. 



V Animal, p. 66. 



a 

 o 



.a 



S 

 s 

 +■» 



o 



I 



S 

 P 



a The columella, in the form of a concave arch, continued with the 



outer lip. PI. 9 } fig. 7. 

 b Calcar, Montf. Flattened; lip sharp, like the rowel of a spur. PI. 9, 



fig. 10. 



c With a small prominence, or vestige of a tooth, towards the base of 

 the columella. 



d Mouth much broader than long ; base concave. PI. 9, fig. 9. 



e Mouth much broader than long ; and the columella in the form of a 



spiral canal. 

 f Turreted. 



g No projection to the columella. 



h Flattened; the exterior angle edged. 



t Flattened ; the lips rounded. 



A Columella with a prominence towards the base. 



/ Columella embattled lengthwise. 



2. Cirrites. Sowerby, 



Conical ; whorls united. 

 PI. 9, fig. 4. 



3. Solarium. (2) Lam. 



Spire like a dilated cone. 

 PI. 9, fig. Hi 



No columella : umbi- 

 licus funnel-shaped. 



A very large umbili- 

 cus, hollowing out the 

 base. 



In the Chalk Marie, 

 under Oolite, and Der 

 b j shire - Peak Lime- 

 stone: 



Marine. 



V. Animal, p. 66. 



4. EUOMPHALITES. Sow- 



erby. 



Rolled almost in the 

 same plane, depressed 

 above. PI. 9, fig. 18, 19. 



5. Ianthina. Lam. 



Concave or largely urn- 

 bilicate underneath. 



In the LimestoneShale ; 

 in the 1st or Upper 

 Grey and in the Peak 

 Limestone of Derby 

 shire. 



Subglobulous, horizon- Columella prolonged Marine. 

 tally volute ; no opercu- beyond the mouth. Mediterranean. Aus- 



lum. PI. 9, fig. 26. tralasia. 



A floating shell. 



V. Animal, p. 67. 



(1) Foss in the London Clay ; Crag Mart; Under Oolite ; Blue Lias ; at Grienon • 

 near Pont Char-train; Longjumeau. The Trochus agglutinaus.. PI 9, fia 8 is re- 

 markable for its habit of agglutinating to, and even of incorporating with, its 

 shell during the growth, small pebbles, fragments of other shells, sand, etc etc 

 It often covers ttc umbilicus with a testaceous plate. A fossil variety of this cu-' 

 nous shell, wh,ch inhabits the^seas of South America, is found at Grignon 



W Foss. in the London Clay ; Purbceh Limestone ; at Grignon. 



