new or little-known Goniatite3/)'o»j Ireland. 433 



defined ; sides feebly convex, a little flattened near the 

 umbilicus, and beconiin/^ more flattened and convergent on 

 the body-chamber; umbilical zone well defined, narrow, 

 almost perpendicular to the plane of symmetry of the shell. 

 Body-cliamber occupying nearly a complete whorl; aperture 

 not seen, but the peristome (judging by the lines of growth) 

 probably with a broad feeble lateral crest and a fairly deep 



Fi-. 2. 



Perici/chis irapezoidah>i. — Lateral view of the type specimen, showing 

 the ornaments of the shell, as well as some of the septa of the earlier 

 portion of theouter whorl. Carboniferous Limestone : St. Doulag'h's, 

 Co. Dublin, Ireland. Drawn from an eximple in the collection of 

 Dr. A. H. Foord, F.G.S. About three fifths uatur.d size. 



hyponomic sijius. Depth of chambers not seen ; suture-line 

 only imperfectly seen. Test ornamented with narrow promi- 

 nent ribs, which pass obliquely backward from the umbilical 

 margin, cross the lateral area in a feeble anteriorly convex 

 curve, and form on the periphery a fairly deep and wide 

 (hyponomic) sinus ; interspaces flat, nearly twice as wide as 

 the ribs; the whole surface of the ribs and interspaces (when 

 well preserved) with fine close-set lines of growth, especially 

 on the body-chamber. The outer whorl with numerous (nine 

 or ten) constrictions, following the course of the ornaments 



