THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE II. VOL. II. 



No. VI— JUNE, 1875. 



OBIGIUAL AKTICLBS. 



I. — On some TJndescribed Carboniferous Fossils. 



By R. Etheridge, Jim., F.G.S. ; 

 Of the Geological Survey of Scotland. 



(PLATE VIII.) 



THE following species of Modiola is common to the Carboniferous 

 Limestone series of England and Scotland, and appears to have 

 been hitherto undescribed from them, although it may, perhaps, be 

 identical with an American Sub-carboniferous species. 



Genus Modiola. 

 Modiola lithodomoides, 1 sp. nov. PL VIII. Figs. 1 and 2. 



Lithodomus daotyloides, Huxley and Etheridge's Cat. Foss. Mus. Pract. Geol. 



1865, p. 110 (nonM'Coy). 

 Lithodomus dactyloides, R. Etheridge, jun., Mem. Geol. Survey, Expl. 22, Scot- 

 land, 1872, p. 43 (non M'Coy). 

 [Compare, — Lithophaga lingualis, Meek and "Worthen, Geol. Rep. Illinois, 1868, 

 vol. iii. p. 536, t. 19, f. 1 (and f. 2 ?), (non Phillips).] 



Specific characters. — Shell much elongated, and convex ante- 

 riorly, compressed posteriorly ; beaks quite anterior, and terminal, 

 bluntly pointed; anterior end somewhat narrowed, convex in the 

 umbonal region, and compressed towards the ventral margin; posterior 

 end expanded and wider than the anterior, much compressed laterally ; 

 dorsal margin straight ; ventral margin curved, at the anterior end 

 convex, gently and slightly concave in the middle, and convex at the 

 posterior end ; the valves are gibbous along a line nearest to the 

 dorsal margin, backwards to the posterior end, but which gradually 

 descends until it becomes lost in the expanded portion of the latter ; 

 the greatest convexity is about the middle of the shell, but if any- 

 thing a little anterior ; the shell is thin, and has a surface ornamen- 

 tation consisting of exceedingly fine, closely set, and regular lines, 

 with, here and there, an occasional wrinkle, especially towards the 

 ventral margin. 



Observations. — This is an exceedingly graceful and well-marked 

 shell. The specimens which have come under my notice vary a little 

 amongst themselves ; thus, in the majority the dorsal margin is 

 straight, but in one specimen there is a tendency to become a little 

 arched. The amount of the concavity in the central part of the ventral 

 margin and the expansion of the posterior end are also variable. From 

 1 From its general resemblance to the genus Lithodomus. 



DECADE II. — VOL. II. — NO. VI. 16 



