6ob 



YORKSHIRE TYPE AMMONITES 



May 



60. AMMONITES CROSBEYI, 

 (Plate LX) 



Simpson 



Original Description 

 " 33. A[mmonites] crosbeyi. [M. Simpson, 1843, p. 22.] 



["I. Without a dorsal keel or furrow. 

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



" Thickish ; volutions 4, inner ones ^ concealed : radii numerous, 

 slender, annular, generally split in two in passing over the back ; inner 

 margin of the whorls slightly rounded, and overhanging the next ; 

 aperture one-half of a regular ellipse ; diameter 3 inches. 



" This may be distinguished from the last | A. semicelatus], by the 

 inner margin of the whorls overhanging the succeeding ones, as well as 

 by its thickness, and the more r^pid diminution of the whorls. It is 

 at present a rare shell, and was discovered by Thomas Crosby, who has 

 long been a diligent collector of fossils, and is intimately acquainted 

 with every stratum of the neighbourhood." 



Additional Details 



Simpson, 1855, 58, second paragraph omitted. Description placed 

 under heading : — 



" The following species, to the end of the section, have all a family 

 resemblance to A. communis : — Whorls narrow, exposed, with numerous 

 slender, annular ribs, which generally split in two on the back." p. 30. 



Simpson, 1884, 90, the same. 



Remarks 



Stages, conch, serpcnticone ; periphery, i ; ornament 4 (4c ?). 



Ribs septate, sometimes single, mostly bifurcate, sometimes second- 

 aries intercalated. No iibulation visible ; but inner whorls obscure. 

 Outer whorl beginning to narrow and contract. 



Genus, Crcloceras, Hyatt (Gen. iv) ; family, Dactyloid;e, Hyatt. 

 Geological position may be lilli zone, if Wright's sj)ecies, quoted on 

 opposite page, is the young state : the locahty and stratum given for that 

 indicate lilli zone. 



Result 



CcELOCERAS CROSBEYI, SiMPSON sp. 1843, Whitbian, [lilli zone ? 

 near Whitby]. 



