AVICULOPECTEN SUBCONOIDEUS. 77 



the centre of the binge-line. The anterior ear of the right valve short, triangular, 

 its upper margin prolonged to a point, separated from the valve by a deep, wide 

 byssal notch ; the posterior ear flattened, its posterior border falcate, not separated 

 from the valve by a groove, but formed by a gradual compression of the valve. 

 The left anterior ear better defined, compressed, its upper border prolonged 

 and pointed, its anterior margin falcate. The left posterior ear as in the right 

 valve. 



Interior. — The hinge-plate is broadly triangular, crossed by transverse grooves. 

 Internal surface smooth near the umbo, but with radiating ribs and sulci near the 

 periphery. Adductor scar large, rounded, placed high up and posterior to the 

 middle line. 



Exterior. — The surfaces of the left valve and both ears are marked by many 

 close, raised, flattened, unequal, radiating ribs, which are not so close or numerous 

 on the ears, crossed here and there by concentric lines of growth more frequent 

 on the ears. The right valve has the same character of ornament, but is much 

 less strongly marked, and the anterior ear is almost free from radiating lines. 



Dimensions. — PI. XVII, tig. •">, a left valve, measures — 



Antero-posteriorly . . . :>2 mm. 



Dorso-ventrally . . . 35 mm. 



Length of hinge-line . . . .27 mm. 



Localities. — Scotland : Calciferous Sandstone series of Newton Quarry, Knock- 

 hill, Fife; Wardie Shales, Craigleith Quarry; Carboniferous Limestone series, 

 West Quarry, Salton, and Beucloich, Millburn, Lennoxtown ; Grawkhall Scar, 

 Kirtle Water, Ecclefechan; Whitefield Quarry, west of Machbie Hill Station. 

 Ireland: Carboniferous Sandstone, Carnteel, co. Tyrone; Carboniferous Slate, 

 Lehenagh, co. Cork. 



Observations. — .!. subconoideus is fairly common in the shell beds of Newton 

 Quarry, Knockhill, Fife, whence Air. Etheridge obtained the specimens he described 

 and figured. The types are small, however, and the left valve is a cast of the 

 interior, while the right valve has only the posterior ear not freed from the matrix. 

 The figured specimens (PI. XVII, figs. 1 — 3) are in the Museum of the Geo- 

 logical Survey of Scotland. Mr. Etheridge was correct in separating this species 

 from Pecten conoideus, M'Coy, which is distinct. This species passes up into the 

 Carboniferous Limestone series. It has been reported from several localities 

 (' Mem. Geol. Surv. Scotland;' 'Geol. Eastern Fife,' 1902, p. 368) both in the 

 Calciferous Sandstone and Carboniferous Limestone series of the east of Scotland. 

 When large and crushed the shell becomes somewhat distorted, and the lint.' 

 limiting the ears is obliterated. 



