356 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 15, 



in the * Geology of Russia,' wliieli do not exhibit the well-defined 

 deltidium and foramen characteristic of the subgenus and species. 

 M. de Koninck hkewise informs me that in Belgium his Sp. Murchi- 

 sonianus is always found in the Upper Devonian beds immediately 

 under the carboniferous strata, and he beHeves this to be also the 

 case in China ; but that the species he has described from the pro- 

 vince of Yuennam belongs to a bed rather lower down, viz. to the age 

 of the Eifel. 



3. Rhynchonella Hanburii, Davidson. Pl. XV. figs. 10, 11. 



Shell irregularly triangular, inequivalve, wider than long ; beak 

 acute, but slightly produced, incurved, and leaving a very small space 

 for the passage of the peduncle. Socket or dorsal valve most convex, 

 presenting a regular convex curve from the^ umbo to the front, where 

 the shell attains its greatest elevation. The valves are ornamented 

 by from eleven to twelve large ribs, but which only extend over the 

 frontal and lateral half of the shell ; three of these form a more or 

 less elevated mesial fold, and in the ventral valve two commonly oc- 

 cupy the sinus : besides these the whole external surface is furrowed 

 by small radiating striae. Shell-structure impunctate : dimensions 

 taken from two specimens, — 



Length 8^, width 9^, depth 8 lines. 



Obs. — Four or five examples of this species have been sent from 

 Kwang-si, all exactly agreeing in external character and presenting 

 the same number of plaits. The occurrence of strise and plaits on 

 the same shell is common to many forms, especially among the 

 oolitic and cretaceous species, but more rarely so among the hitherto 

 discovered palaeozoic forms. The Rh. Haiiburii is distinguished from 

 the Rh. Schnurii by its triangular shape ; the Prussian species being 

 more square and globose, and differing likewise in the number of its 

 large plaits ; but the same character of striation occurs in these two 

 species, as well as in the Rh, Wrightii from the inferior oolite of 

 Cheltenham. In the young state, as seen by fig. 1 1, none of the 

 large subsequent plications can be traced. 



4. Productus subaculeatus, Murchison. Pl. XV. fig. 12. 



Productus subaculeatus, Murchison, Bulletin de la Soc. Geol. de 



France, vol. xi. pl. 2. fig. 9 (1840)*. 

 , De Koninck, Monog. du Genre Productus, p. 142. pl. 15. 



fig. 4. 



Shell semicircular ; ventral valve regularly convex, globose, vnth 

 small auricular expansions ; hinge-line straight, almost as wide as the 

 shell ; beak considerably incurved ; dorsal valve regularly concave ; 



* Refer likewise to a very interesting paper on this species by M. Bouchard, 

 published in the Annales des Sciences Nat. Paris, Sept. 1842. Some examples 

 fi-ora Ferques have attained dimensions twice as great as those hitherto obtained 

 from China. 



