264 CARBONIFEROUS LIMESTONE FOSSILS. 



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 lines, at inner edge 1 inch 10 lines, diameter of umbilicus 

 about 3~ 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 th^ N. tuberculatum. I have only indistinctly seen the 

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

 close. The position of the siphon is unknown. 



Very rare in the carboniferous limestone of Derbyshire. 



[Col. University of Cambridge.) 



Orthoceras [Cycloceras) Flemingi (M^Coy). 



Desc. Very gradually tapering ; section (? broad oval), siphon 

 subcentral, large, slightly excentric ; septa numerous, mode- 

 rately convex, one coinciding with each of the external rings. 

 Surface girt with close, obtuse, prominent, transverse rings, 

 little more than their own diameter apart, undulated by about 

 fourteen or fifteen strong longitudinal costse, slightly further 

 apart than the transverse rings, so that the oblong intervening 

 spaces are wider than long, and nearly equalling them in 

 thickness, both transverse rings and intervening spaces marked 

 by strong transverse imbricating striae, six or seven between 

 the centre of one transverse ring and the next. A specimen 

 5 lines long and 2 lines in diameter at the smaller end has 

 twelve rings. 



This species can only be confounded with the 0. (C) rugosum 

 of Flem., from which it is distinguished by its much more nu- 

 merous and closer rings, fewer and larger longitudinal costse, 

 stronger transverse strise, and large siphon far removed from the 

 marffin. 



