69b YORKSHIRE TYPE AMMONITES— II May 



69. AMMONITES FOVEATUS/ Simpson 

 (Plate LXIX) 



Original Description 

 " 69. A[mmonites] foveatus. [M. Simpson, 1855, p. 57.] 



[" 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. 50.] 



" Thick ; volutions 6, well exposed, outer whorl J the diameter, 

 sides and back rounded ; umbilicus deep ; radii annular, split in two 

 before they pass over the back, strong, scarce equal to the intervening 

 concave furrows ; aperture transverse ; diameter ij inch. 



" In general form this ammonite resembles A. subarmatus, but quite 

 free from spines or tubercles, and the whorls diminish much more rapidly 

 than in A. crassus, forming a deeper and larger umbilicus. The shell, 

 where it remains, is of a light-brown colour and very smooth and shining ; 

 the radii are rounded, but on the cast they are flatted, especially on the 

 back. The ramifications of the septa are obtusely pointed, and by no 

 means so crowded as in many species. It is very pyritous, and appears 

 to be from the lower lias." 



Additional Details 



Simpson, 1884, p. 89, adds to end of 1st par. " U.L.," and omits 

 last sentence of 2nd paragraph. 



Remarks 



Proportions, 34, 30, 56, 45 : Subplaty-, subextremipachygyral, 

 perlatumbilicate. 



Stages, conch, serpenticone ; periphery, 1 ; ornament, 4c. The 

 inner whorls are craterumbilicate, and appear to be coronetted, but 

 without fibulation : tubercles lost on outer whorls. Ribs mostly bifur- 

 cate, and on venter distinctly septate (" flatted," Simpson, alluding to 

 impressions of the partitions). Suture-line not sufficiently clear for 

 delineation, .but seems to be of the pattern of that shown by d'Orbigny 

 for A. raquinianus. 



Genus, Cceloceras, Hyatt ; family Dactyloidae, Hyatt. Geological 

 position, presumably Alum Shale— from condition. 



Result 



Geloceras foveatum, Simpson sp. 1855, Whitbian, [subcarinatum 

 zone ?] near Whitby 



