AVICULOPECTEN SEDaWICKT. 101 



line straight, of moderate length. Umbones small, acute, central. Bars large, 

 well denned, compressed, the anterior the larger; that of the right valve deeply 

 slit for the byssus ; the posterior ear elongate, narrow, and acutely pointed. Shell 

 very thin. 



Interior. — Seems to be normal, smooth, without traces of the concentric 

 sulci. 



Exterior. — The surface is smooth, crossed by two or three distant, deep sulci, the 

 upper margin of which is at times converted into a concentric ridge. 



Dimensions. — PI. XVIII, fig. 10, a right valve, measures — 



Antero-posteriorly .... !> mm. 



Dorso-ventrally . . . .10 mm. 



Locality. — Ireland: the Carboniferous Limestone of Little Island, co. Cork. 



Observations. — Phillips's poor figure is accompanied by an even more meagre 

 description, which reads as follows : — " This has scarcely distinguishable characters, 

 yet contrasts with the others by its smooth concentric furrows ;" and it is on the 

 latter character alone that I have considered it well to retain the species. 

 M'Coy's description is a little more detailed. 



I refer to A. deomatus a number of specimens from Little Island, co. Cork, in 

 the cabinet of Mr. Joseph Wright, of Belfast. The majority of the specimens 

 consist of right valves, but the left valve is represented. The long hinge-line 

 and pointed ears demonstrate the affinity of the shell to Aviculopecten. 



A. deomatus is easily diagnosed from A. Sedgwichi, the angular concentric 

 ridges of the latter being absent, and the valve being more orbicular and less 

 regularly ovate. A. interlineatus, Meek and Worthen, is very similar in appear- 

 ance to A. deomatus. 



A.VICULOPECTEN Sedgwicki, M'Coy, sp., 1814. Plate XVI, figs. 28—33. 



Pecten Sedgwickii, M'Coy, 1844. Syn<>i>w. Carb. Foss. Ireland, p. 99, pi. xiv, 



fig. 4. 

 Aviculopecten Sedgwickii, Morris, L854. (Jut. Brit. Foss., 2nd edit., p. 105. 



Specific Characters. — Shell small, longitudinally ovate, the left valve moderately 

 convex, the right flattened. Ears well marked, the anterior depressed, rolled, and 

 pointed, the posterior rapidly compressed and pointed. The hinge-line straight and 

 long, the umbo in the left valve gibbose, pointed, and raised above the opposite 

 valve; the right umbo small, flattened, and placed below the left, below which there 

 seems to be a notch to receive it when the valves were open. 



interior. — Unknown. 



