DEVONIAN FOSSILS. 239 



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

 width of mouth at edge of umbilicus y^^, width of periphery 

 about yVo . 



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

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

 most allied to the Clymenia 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 w^hich there is not 

 the slightest trace on the present fossils. I have seen traces 

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

 sionally noticed on the other species. 



Very rare in the Upper Devonian limestone of S. Petherwin. 



{Col. University of Cambridge.) 



Clymenia 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 super- 

 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 

 backwards and then forwards again to the edge of the umbi- 

 licus, forming an obtusely rounded first sinus, which extends 

 backwards about half the space between the septa farther than 

 the middle portion. Diameter 9 lines, proportional diameter 

 of umbilicus YwUf ^^ ^^^^ whorl y*y^j, width of mouth y^^^. 

 This species belongs to that very restricted first group of Cly- 

 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 differs 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 difi'er 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 

 £^cross the outer half of the sides and periphery^ forming no 



