AVICULOPECTEN PERRADIATl S. 87 



Natural History Museum, but this can hardly have served for the figure, as the 

 ears arc not well developed from the matrix, the anterior not being at all visible. 



Two other figures of a Pectiniform shell are given in the same work as 

 P. scalaris. These I consider to represent the same species as the former shell, 

 the only apparent difference in the figures being the number of ribs; but the 

 descriptions of both shells state that the number is fifteen in each case. 



In 1002 (lor. cit.) I figured both valves of a little shell from a richly fossiliferous 

 bed on Congleton Edge, about 500 feet below the Third Millstone Grit, as Salter's 

 species, A. fibrillosus. Right and left valves occur close behind each other on the 

 same slab; but I am convinced that my shells are identical with A. gent His, and 

 that I was wrong to trust to the published figure of Salter's species, from which it 

 is quite distinct, as may be seen on reference to the figures of Psendamusium 

 fibrUlosum now given (PI. XVI, figs. 16 — 22). 



AVICULOPECTEN PERRADIATUS, de Koninck, 1885. Plate XV, figs. 10 — 18. 



Aviculopecten perradiatus, de Koninck, 1885. Ami. Mus. Roy. d'Hist. Nat, 



Belg., torn, xi, p. 229, pi. xxxiv, figs. 12, 13. 



Specific Characters. — Shell small, suborbicular, left valve very gently convex. 

 The margin of the valve almost circular from ear to ear. The hinge-line straight. 

 Umbones small, pointed, subcentral. Ears well defined ; the left anterior ear 

 triangular, narrow, and small, well marked off from the valve by a groove, its 

 anterior margin gently rounded ; the left posterior ear longer and deeper, and 

 larger than the anterior, pointed, its posterior margin falcate. A shallow oblique 

 depression in the valve both in front and behind just below the folds for dividing 

 off each ear. 



Interior. — Unknown. 



Exterior. — The surface of the left valve is ornamented with numerous, fine, 

 unequal, radiating ribs, secondary ribs arising between each primary pair. The 

 ribs are traversed by four concentric lines of growth and are finely reticulate. 

 Both ears arc crossed by several radiating ribs decussated by lines of growth. 



Dimensions. — PI. XV, fig. 17, a specimen in the collection of the Geological 

 Survey Museum, Jermyn Street, from Narrowdale, measures — 



Antero-posteriorly . . . .17 mm. 



Dorso-ventrally . . . .10 mm. 



Localities. — The Carboniferous Limestone of Narrowdale, Staffordshire, and 

 Park Hill, Derbyshire. 



Obser cations.- — This species was founded by de Koninck on a specimen from the 

 Limestone of Vise, and his description is very full and accurate, with a good 



