448 Mr. G. C. Crick on some 



the diameter of the shell in width. Whorl lunate in cross- 

 section, the height about thiee fourths of the width ; indented 

 to nearly one half of its height by the preceding whorl ; peri- 

 phery broadly convex, imperfectly defined; sides convex ; 

 umbilical zone well defined, narrow, almost perpendicular to 

 the plane of symmetry of the shell. Body-chamber occupying 

 nearly the whole of the last whorl ; aperture not seen, but 

 (judging by the growth-lines) the peristome probably with 

 only a very feeble crest near the edge of the umbilicus, and 

 with a very wide and shallow hyponomic sinus. Chambers 

 shallow; suture-line as in fig. 13. Test nearly smooth, with 



Fig. 13. 



Glyphioceras corpulentum. — Suture-line drawn from an example in the 

 collection of Dr. A. H. Foord, F.G.S. Carboniferous Limestone : 

 St. Doulagh's, Co. Dublin, Ireland. Natural size. 



fine subregular raised lines, which become more distinct in 

 the adult ; these pass obliquely backward from the umbilicus 

 as far as the margin of the periphery, where they assume a 

 nearly radial direction, and cross the periphery in a very wide 

 and shallow hyponomic sinus ; in the adult the periphery 

 bears eight or nine obscure rather widely spaced longitudinal 

 lines. 



Dimensions. 



(i.) (ii.) 



Diameter of shell 64 mm. (100) 95 mm. (100) 



Width of umbilicus (at suture 



of shell) 15 5 „ (24-2) 22 „ (23-1) 



Width of umbilicus (at its 



margin) 21 „ (32-8) 25 „ (26-3) 



Height of outer whorl 27 „ (42-1) 45 „ (47'3) 



Ditto above preceding whorl about 16-5 ,, (257) about 20 „ (21-0) 



Thickness of outer whorl 40-5 „ (63-2) 58 „ (610) 



Remarks. The two examples of this species that I have 

 seen are in the collection of Dr. A. H. Foord. Their 

 dimensions are given above. The larger specimen (ii.) shows 

 the form of the inner whorls and is regarded as the type, the 

 smaller example (i.) exhibits the suture-line. 



Affinities and Differences. This species can be readily 

 recognized by the nature of its ornaments and by the inflation 

 of its whorls. 



