7 2b YORKSHIRE TYPE AMMONITES— II May 



72. AMMONITES ACULEATUS, Simpson 

 (Plates LXXIIa, b, c) 



Original Description 

 "44. A[mmonites] aculeatus. [M. Simpson, 1843, p. 27.] 



["I. Without a dorsal keel or furrow." p. 7. 

 " b. Armed with spines or distinct tubercles." p. 22.] 



" Volutions 6, exposed ; obsoletely radiated ; armed with a row of 

 moderate, pointed spines ; striae numerous, undulating, annular ; aperture 

 circular ; diameter 10 inches. 



" This fine ammonite is at present in the possession of Mr. Andrew. 

 A smaller specimen in the Whitby Museum (diameter 7 inches) displays 

 the edges of the septa, which are exceedingly fine and intricate ; some 

 are pointed, others are rounded, crowding the whole surface of the whorls 

 with their delicate meanderings." 



Additional Details 



Simpson, 1855, 66, leaves out first sentence of 2nd paragraph. Begins 

 second sentence, " The edges of the septa are exceedingly fine snd [and] 

 intricate," and continues as 1843. Adds for 3rd par. " They vary 

 much in the length and number of the spines. — Brassy Bed L.L. ; R.H. 

 Bay." 



Simpson, 1884, 99, the same as 1855, except that last seven words 

 are placed after 1st par. Misprint corrected. 



Remarks 

 Proportions : — 180, 31, 35, 43 ( 

 80, 33, 36, 43 I 

 Subplaty-, pachygyral, perlatumbilicate. 

 Stages, conch, serpenticone ; periphery, 1 ; ornament, 5*. 

 To diameter 14 mm. imperfect ; to about 22 mm. pettos form, closely 

 spinicostate ; to 125 mm. squared whorls, parvicostate, much prorsi- 

 radiate ; with irregular small spines, increasing in size with age ; onwards, 

 whorls becoming somewhat divergent, costae wave-like and rarer, but 

 not prominent, carrying large spines. All spines septate, the large leave 

 large plate-like markings (basal septa). Periphery flatly arched, costate. 

 Suture-line very highly complicated, not well exposed. 



Genus, Deroceras, Hyatt ; family Deroceratidae. Geological position, 

 Brassy Bed is presumably L.L. y (1884, p. xx). 



The specimen, No. 177, is the paratype described by Simpson. 

 Search for the large example, which may have been sold away from 

 Whitby by Mr. Andrew, is hereby requested. 



Result 



Deroceras aculeatum, Simpson sp. 1843, Charmouthian, armatum 

 zone, Robin Hood's Bay, near Whitby. 



