346 R. Mheridge, Jun. — Contributions to Pakeontology. 



and would tlierefoi-e remain in the genus Pecten, as originally placed 

 by their respective describers, rather than Aviculopecten, as all such 

 shells have been termed since McCoy first described the latter genus. 

 This I hope to make the subject of a future communication. 



An exceedingly graceful species of Avicidopecten, which I had 

 previously laid aside as different from any described form I could 

 meet with, has lately come under my notice in considerable quantities 

 from certain of the Lanarkshire Carboniferous beds. I propose to 

 call this 



Aviculopecten ornatiis, sp. nov., PL XII., Fig. 2. 



Sp. chars. — Longitudinally obovate, slightly convex, flattening 

 towards the margin, slightly inequilateral ; ears very uneqiial ; an- 

 terior small, triangular, divided from the body of the shell, and 

 ornamented with strong radiating ridges, which are crossed by fine 

 delicate strige ; posterior ear large, rectangular, but in perfect 

 specimens pointed, as shown by the curving of the lines of 

 growth ; hinge-line a little less than the width of the shell ; shell 

 thin ; ornamentation very characteristic, concentrically marked with 

 exceedingly close lines of growth, which on the anterior side only 

 are crossed by very delicate and flexuous radiating striee, close to- 

 gether. Both valves appear to be alike. 



With the exception of the small anterior ear, A. ornatus resembles 

 to a certain extent A. (Meleagrina) rigida,^ McCoy, in general outline, 

 but differs in numerous minutiae, and forms one of a somewhat large 

 series of thin-shelled Aviculopectens, common in Scotch Carboniferous 

 rocks, more numerous in individuals than species, comprising such 

 as A. subelongatus, McCoy, A. {Pecten">) deornatus, Phil., Pecten 

 (Amusium) Sowerhii, McCoy, and a few others. 



Locality. — Kinghorn, near Burntisland, Fife: in shale of the 

 Lower Limestone Series. Cabinet of Mr. D. J. Brown, Edinburgh. 

 Also found by the Geological Survey collectors at many localities in 

 Lanarkshire (see forthcoming Explanation to Sheet 23, Geol. Survey 

 of Scotland). 



An equally interesting series of shells, although not nearly so 

 numerous in the matter of species, yet quite so as regards individuals, 

 are the Carboniferous Nuculidce, comprising the genera Niicula and 

 Leda. By the late Mr. J. W. Salter, the greater^ portion of the 

 Paleeozoic species of these genera were merged in his Ctenodonta,^ a 

 genus originally instituted for the reception of certain North Ameri- 

 can species of Arca,^ Nucula, etc. Salter's Ctenodonta possesses an 

 external ligament and hinge teeth, but no central cartilage-pit, 

 and, so far as Silurian species are concerned, is a good genus; 

 but I think that many of the Carboniferous Nuculie and Ledcs re- 

 ferred by that lamented paleeontologist to Ctenodonta,^ were so placed 

 hastily, and without sufficient consideration. I have examined a 

 very large number of these little shells, both from English and 



1 McCoy, I.e., p. 80, pi. 13, f. 16. 



2 Geol. Surv. Canada, Deeade 1, p. 34.— Mems. Geol. Survey, vol. 3, app. p. 345. 



3 Brit. Ass. Rpt. 1851, Trans. Sect. p. 63. 



* Mems. Geol. Survey, Country around Oldham, Sheet 88 S.W., p. 65. 



