488 Prof. F. M'Coy on some new Devonian Fossils. 



meter 1 inch 3 lines, proportional diameter of last whorl y'^^, 

 width of mouth at edge of umhilicus y^^'^, width of periphery 

 ahout yj/o. 



This species is easily distinguished from all others by the re- 

 markably defined, nearly square form of the lateral lobe. It is 

 most allied to the Chjmenia striata, Miinster, from which it is 

 easily distinguished by the very obtusely rounded, obscurely de- 

 fined first sinus, and the regular, almost square-formed lobe and 

 the scarcely curved margin of the second sinus; the cast of that 

 species is also marked by sigmoid ridges, of which there is not 

 the slightest trace on the second species. I have seen traces 

 both of the evanescent thread-like middle and lateral keels occa- 

 sionally noticed on the other species. 



Very rare in tlie limestone of S. Petherwin, 



[Col. University of Cambridge.) 



Chjmenia Pattisoni (M'Coy). 



Sp. Char. Discoid, compressed, of about five whorls, rather more 

 than one-third of each being concealed by the preceding turn ; 

 section of the whorls semielliptical, greatest thickness near the 

 edge of the umbilicus, which is considerably wider than the 

 whorl; sides very slightly convex, gradually converging to the 

 obtusely rounded periphery, to which there is often supei'- 

 added a very fine thread-like mesial keel and two lateral ones ; 

 surface finely striated transversely ; siphon large, close to the 

 inner margin ; septa about one-third the width of the side 

 apart, with the middle portion nearly transverse, no lateral 

 lobe, but the edges after about the middle of the side arching 

 backw^ards and then forwards again to the edge of the umbi- 

 licus, forming an obtusely rounded first sinus, w^hich extends 

 backwards about half the space between the septa farther than 

 the middle portion. Diameter 9 lines, proportional diameter 

 of umbilicus y\j^^, of last whorl y'^^^ ; widtli of mouth -YTyQ. 



This species belongs to that very restricted first group of C/y- 

 menia according to Miinster, in which the edges of the septa are 

 only slightly arched ; it is most nearly allied to the C. com^ 

 pressa, Miinster, from which however, on comparing with au- 

 thentic specimens, I find it diffl>rs by the great size of the umbi- 

 licus, which in that species is much less than the last whorl, form- 

 ing scarcely y%'^ of the entire diameter. The septa difiier from 

 all of this group in the greater forward curvature of the umbilical 

 end of the edge of the septa, thus forming a distinct rounded 

 sinus, from which the edge passes with very little curvature 

 across the outer half of the sides and peripheiy, forming no 



