SPIRIFERA. 23 



did not present any interior, but the external characters are so exactly similar to some 

 Russian examples from the Donetz at Moscow and Viterga, that I have felt no doubt 

 as to their identity. Sp. mosquensis is also very variable in its proportions, and (as 

 observed by one of the above-named authors) shows a marked tendency to elongation, 

 especially in the adult condition. Thus, some Russian specimens measured 27 lines 

 in length by 22 in breadth ; and a Belgian example, figured by M. De Koninck, attained 

 still larger dimensions (38 lines in length by 39 in breadth). 



Sp. mosquensis is distinguished from Sp. striata by its much more elongated appear" 

 ance; from Sp). bisulcata it is separable by its more numerous and smaller ribs, and 

 approaches most to Sp. humerosa of Phillips, but from which it is likewise distinguished 

 by a smaller and less inflated beak than that peculiar to Phillips's species. 



Both MM. De Koninck and De Verneuil have remarked that the shell under descrip- 

 tion must not be confounded with that named Sp. Sowerbyi by Defrance, in the 

 ' Dictionnaire des Sciences Naturelles,' vol. 50, p. 295, pl.lxxvi, fig. 2, which belongs to a 

 specimen of A. reticulata of Linnseus. 



Loc. In England it is found near Bristol. A specimen is also labelled Derbyshire 

 in the Cambridge Museum. In Ireland it has been collected from Little Ireland ; but I 

 have not hitherto observed any example from Scotland. In Belgium it is stated by 

 M. De Koninck to occur abundantly near Tournay, d'Ath, de Soignies, de Felay, &c. 

 Fischer de Waldheim obtained it from a white Carboniferous limestone at Grigorievo, 

 Podolsk, Miatchkovo, and other localities in the neighbourhood of Moscow. M. De 

 Verneuil found it to be one of the most characteristic shells of the middle beds of the 

 Carboniferous system throughout Russia and Oural, being there associated with Productus 

 gigas and other shells. 



Spirifera humerosa, Phillips. Plate IV, figs. 15, 16. 



Spirifera humerosa, Phillips. Geol. of Yorkshire, vol. ii, p. 218, pi. xi, fig. 8. 



Spec. Char. A ponderous shell, variable in shape, sometimes transverse, but more 

 often elongated ; valves convex ; beak large and considerably inflated, much incurved, 

 with a wide, shallow sinus, extending from the extremity of the beak to the front. Hinge- 

 line shorter than the greatest width of the shell. Area narrow. Dorsal valve convex, with 

 a produced, rather angular mesial fold ; frontal wave strongly marked, the margin of the 

 sinus indenting to a considerable extent the corresponding portion of the dorsal valve. 

 Surface ornamented by numerous small ribs, which augment rapidly from numerous 

 intercalations ; the ribs are more or less flattened, especially on the mesial fold, and are 

 at the same time intersected by numerous concentric lines or ridges of growth. 

 Dimensions very variable. 



Length 2 inches 7 lines, width 2 inches 2| lines, depth 1 inch 6| lines. 

 „ 2 inches, „ 2 inches 6 lines, „ 1 inch 6 lines. 



