12 E. ETHERIDGE, JTJN., ON LOWER-CARBONIFEROUS INVERTEBRATA. 



fine close concentric strise, or else toothed, especially on the only 

 remaining ear. 



Loc. and Horizon. In shale, with other marine fossils, at Wood- 

 hall Mill, as before. 



Genus Anthracoptera, Salter. 



Anthracoptera, Salter, 1862, Mem. Geol. Survey, Country around 

 Wigan, p. 37. 



Gen. char. Shell aviculiform, very slightly inequivalve, with a 

 slight byssal notch in both valves; left valve the most convex. 

 Hinge-line with a thickened margin, but no hinge-plate of any kind ; 

 there is an obscure tooth in the anterior part of the hinge, but no 

 lateral teeth. Posterior adductor scar large and subcentral ; ante- 

 rior scar small, umbonal, with at least two supplementary scars ; 

 shell thin, with a puckered or plaited epidermis. (Salter.) 



Obs. The genus Anthracoptera was proposed by the late Mr. 

 Salter to include numerous Coal-measure shells " hitherto called 

 Myalina or Avicula with doubt, but evidently distinct from one 

 and the other of these genera. They have not the unequal valves 

 of Avicula nor the striated hinge-plate of Myalina, nor indeed any 

 hinge-plate at all." I now propose to place in this genus, in addi- 

 tion to the Coal-measure fossils for which it was established, some 

 bivalves from the Lower Carboniferous rocks of this neighbourhood, 

 of which the internal characters of the shell, so far as 1 have been 

 able to make them out, appear to have more in common with this 

 genus than with Myalina. About two or three years before Mr. 

 Salter proposed his name, Dr. Dawson established his genus Naia- 

 dites for similar shells, characteristic of the South-Joggins Coal- 

 measures, Nova Scotia. In a paper on " Fossil Shells from the 

 Coal-measures of Nova Scotia"*, Mr. Salter pointed out the synonymy 

 of the two names, and claimed for his own precedence over that 

 of Dr. Dawson on the ground of more complete description. An- 

 thracoptera appears to have been regarded by Salter as one of 

 either the Aviculidae or Mytilidse, whilst by Dr. Geinitz the typical 

 American species, A. (Naiadites) carbonaria, Dawson, is looked 

 upon as a Dreissena f . The affinity of these shells has been dis- 

 cussed by Dr. Dawson at some length ; he considers them to be 

 brackish- water shells allied to the Mytilidae, or embryonic forms of 

 Unionidse J, and states that the structure of the shell is similar to 

 that of the latter family. 



Anthracoptera ? obesa, sp. nov. PL I. figs. 12, 13 (& 14 ?). 



Sp. char. Trigonal, very gibbous, inequality of the valves distinctly 

 marked; anterior side pointed, well marked, and defined by the 

 byssal furrow in each valve ; posterior side but little flattened, its 



* Quart. Journ. Geol. Soc. xix. p. 80. 



t N. Jahrbuch, 1864, p. 654 ; Gteol. Mag. 1865, ii. p. 205. 



X Acadian Geology, 1867, p. 203. 



