Cb YORKSHIRE TYPE AMMONITES Dec. 



6. AMMONITES RESUPINATUS, Simpson 

 (Plate VI) 



Original Description 

 " 22. A[mmonites] resupinatus. \M.. Simpson, 1843, pp. 15, 16.] 



[" I. Without a dorsal keel or furrow. 

 " a. No spines." p. 7.] 



" Depressed ; volutions 5, exposed, radii on the outer whorls sharp, 

 prominent, bend from the aperture, separated by wide concave spaces, 

 form sharp points on the outer margin of the whorl, nearly obsolete 

 on the back, absent on the inner whorls ; striae numerous, distinct, 

 rather bent, shell thick ; aperture quadrate ; diameter i inch. 



" This species is smooth and shining, both on the cast and where 

 the shell remains. The block from whence it was extracted is in [p. 16] 

 the Whitby Museum, and was procured from the lower Lias at Robin 

 Hood's Bay." 



Additional Details 



Simpson, 1855, p. 43, the same ; 1884, p. 73 omits " depressed," 

 adds " Ind. 23." 



Remarks 



Stages, conch, serpenticone ; periphery, 2 ; ornament 2, jumping 

 to 5, the inner whorls showing a finely-striate stage. 



The genus would be Agassiceras, Hyatt (Gen. p. H) — family Arietidae. 



The geological position given by Simpson is above the semicosfatus 

 bed : this seems rather too high. Blake, 1876, 288, says, " Zone of 

 A. Bucklandi." 



Result. 



Agassiceras resupinatum, Simpson, sp., 1843, Sinemurian [gnnien- 

 dense-zone\, Robin Hood's Bay, near Whitby. 



