Limestone Fossils. 195 



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

 is 7 inches 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 coincide 

 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 card-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 tuberosum (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- 

 lated into large obtuse tubercles (about 1^ inch from tip to 

 tip on last whorl) ; sides sloping rapidly with slight convexity 

 to the umbilicus ; mouth subquadrate, angles rounded, inner 

 side smaller than the other three. Diameter 7 inches 9 lines, 

 width of last whorl 2 inches 2 lines, width of periphery 2 inches 

 10 Iraes, at inner edge 1 inch 10 lines, diameter of umbihcus 

 about 3i inches. 



. I have not distinctly seen the surface of this very large spe- 

 cies, but it seems to be smooth. The comparative flatness and 

 width of the sides, more quadrate mouth, and deeply concave 

 periphery, easily distinguish it from the N. tuberculatus (Sow.), 

 which is the only allied form. In the figure in the ' Mineral 

 Conchology ' of N. tuberculatus (t. 249) there is an apparent con- 

 cavity of the section of the periphery, but as this did not agree 

 with the inner outline I doubted its correctness, and on writing 

 to Mr. Sowerby he very kindly furnished me with the exact form 

 of the section of the original specimen, proving that the peri- 

 phery is strongly and regularly round, contrasting in the strongest 

 manner with the present species, which also wants the medial 

 line of the N. tuberculatus. I have only indistinctly seen the 

 septa, which seem to be regular, moderately arched, and rather 

 close. The position of the siphon unknown. 



Very rare in the carboniferous limestone of Derbyshire. 



{Col. University of Cambridge.) 



