CARBONIFEROUS LIMESTONE FOSSILS. 263 



the apex its angles would be larger in very young specimens) ; 

 umbilicus very wide, rounded, half exposing all the whorls ; 

 base of body-whorl very convex, rounded, with a very obscure 

 angulation at the edge of the umbilicus ; periphery narrowed, 

 obtusely rounded ; upper surface of the whorls marked with 

 sharp, slightly sigmoid, rather unequal ridges, arched ob- 

 liquely backwards, becoming abruptly very much finer and 

 more numerous on passing the circumference to the base (ten 

 of the upper ridges in two lines on the body-whorl), each 

 separated from the next by a sulcus about its own width. 

 Diameter 10 lines, proportional height of spire y^^, height of 

 last whorl -^j^-^, distance between last and penultimate sutures 

 j^jf-Q, width of umbilicus -^-^\j, width of mouth y^^^ . 



This species is distinguished from its congeners by the beau- 

 tifully sharp costellation, or transverse sculpturing of the whorls 

 of the spire, which abruptly ceases on the base of the body-whorl, 

 or becomes there confounded with the lines of growth. The 

 inner lip is complete, but thin, as in other species of Straparollus, 

 distinguishing them from Platyschisma. 



Rare in the lower carboniferous limestone of Lowick, North- 

 umberland. 



[Col. University of Cambridge.) 



Nautilus t costato-coronatus (M*^Coy). 



, I give this provisional name to a fragment too imperfect to 

 allow of full description, but so strongly marked, and unlike all 

 described types, that I wish to call attention to it. The fragment 

 is 7 lines long, and is divided into seven equal chambers, with 

 simple edges; the surface exposed is the periphery, which is 

 broadly rounded, moderately and evenly convex, the sides divided 

 into large conoidal tubercles, each tubercle on one side coincides 

 with one chamber, and there are two chambers between each 

 pair of tubercles, the width of the periphery in our specimen is 

 6 lines, and it is marked with ten narrow equal cord-like, closely 

 tuberculated ridges separated by slightly wider flat spaces. 



It strongly resembles the N. tuberculatus^ Sow., but is distin- 

 guished by the costellation of the surface. 



Very rare in the carboniferous limestone of Lowick. 



[Col. University of Cambridge.) 



Nautilus tuberosus (M^Coy). 



Desc. Discoid, greatest width of the whorls at the angle bound- 

 ing the periphery, which latter is very wide, moderately con- 

 cave in the middle, and having the angle on each side undu- 



