338 DR WHEELTON HIND ON THE LAMELLIBRANCH AND 



irregular in distribution, and those towards the posterior margin stouter than those in 

 front. Occasionally ribs may bifurcate, but more frequently new ones arise between 

 any pair. These ribs are crossed by fine concentric lines of growth. The ears are 

 almost smooth. 



Dimensions.— PI. I. fig. 1. Specimen No. T2218 B , a right valve, measures: 

 antero-posteriorly, 12 mm. ; dorso-ventrally, 14 mm. 



Localities. — Bed in pit shaft at Castlecary Fireclay Works. 



Observations. — There is one specimen of this shell in the collection which I have 

 referred to Shumard's species. The very elaborate description and excellent figures 

 given by Meek and Hayden leave nothing to be said in addition. The British species 

 most closely related is Paleeolima simplex, Phillips. This shell is less triangular, 

 comparatively broader, and has fewer but broader and less angular radiating ribs. 

 Meek and Hayden, following Shumard, refer their shell to Lima, but I have shown 

 that the Carboniferous forms differ in certain details [Brit. Carb. Lamell., vol. ii. p. 39) 

 from typical Limas, and created the genus to receive them. The occurrence of the 

 genus in rocks of Millstone Grit age in Scotland somewhat extends our knowledge of 

 the vertical range of the genus. 



Limatulina alternata, M'Coy, sp., 1844. (PL I. figs. 9, 10.) 



Limatulina alternata, Hind, 1903, Brit. Carb. Lamell. (Pal. Soc), vol. ii. p. 39, pi. xix. 

 figs. 7-10, 12. 



Seven examples of this shell have been obtained, five of which occurred in an 

 impure ferruginous limestone or cement in the river Avon, between the Railway 

 Viaduct and the outcrop of the Castlecary Limestone, in the county of Linlithgow. 

 Some of the specimens are full grown and show no tendency to dwarfing or senile 

 characters. For further details, my work on Carboniferous lamellibranchs (op. supra 

 cit.) may be consulted. The figured specimens are numbered Tl888 B and Tl818 B . 



Pterinopecten Whitei, Meek, sp., 1872. (PI. I. figs. 11-13.) 



Aviculopecten Whitei, Meek, 1872, Fin. Rep. U.S. Geol. Surv. Nebraska, p. 195, pi. iv. 

 fig. 11, a, b, c. 



Specific Characters. — Shell below medium size, subordinately quadrate, the left 

 valve moderately convex, the right valve flattened. The anterior and lower borders 

 rounded. The posterior bluntly rounded below, slightly sinuous above. The hinge 

 line straight, meeting the posterior border with a well-marked angle. The umbones 

 are small, pointed, flattened, not elevated, placed far forward. The anterior ear is 

 small, somewhat angular, well defined from the valve by a deep sulcus, deeper in the 

 right valve than in the left. There is no posterior ear, but the upper and posterior 

 part is compressed and subalate. The surface is ornamented by flattened, flexuous, 

 radiating ribs, irregular in size, being crowded and narrow anteriorly, broader and 



