PTERONITES. 5 



Derbyshire ; Hill Bolton, and beds above the Underset Limestone, Lunds Gill, 

 Yorkshire ; beds above the Underset Limestone, Farcote Gill, Swartli Fell, AYest- 

 moreland ; Carboniferous Limestone, Poolvash, Isle of Man ; Lowick and Redes- 

 dale Ironstone, Redesdale, Northumberland. Scotland: Gleneartholm, Eskdale, 

 Dmnfriesshire ; Lower Limestone series of Craigenglen, Anchenskeith ; Lngton 

 Water, Waterland ; Gateside, Beith ; Salton. Ireland : Arenaceous Limestone, 

 Kilbride, Ballycastle, co. Mayo. 



Ohserrations. — The type, PI. I, fig. 3, of M'Coy's Pinna luutiai is preserved in 

 the Griffith Collection, Science and Art Museum, Dublin. It is very imperfect and 

 small, but there is no doubt that it is the same species as the shells described later 

 as P. sjjatida by the same author (oj). supra cit.). PI. I, fig. 1, is the type of i'. 

 xpatula, and is preserved in the Woodwardian Museum, Cambridge. This specimen 

 is much crushed and imperfect in front. It would ap])ear, judging from this 

 specimen, that in a very elongate example the slope of the inferior border is much 

 decreased towards the posterior end of the shell, and PI. I, fig. 6, bears out this fact. 

 The latter specimen is crushed, but shows that the shell had a moderately thick 

 periostracum. 



De Koninck describes three species of smooth Pinniform shells, which diifer from 

 each other only in size, convexity, and the angle formed by the upper and lower 

 margins. It is a question whether these differences are of specific value, and are not 

 merely due to growth. The three species are stated to be more or less rare, and to 

 occur in the limestone of Vise. It is, however, true that a certain amount of variability 

 in convexity and angularity is seen to occur, if a large number of specimens from 

 any British locality be examined. None of our specimens give any indication of the 

 peculiar umbones figured by de Koninck, which are considered by him to be so 

 important that the group of shells is placed in the genus Aviculopinna of Meek, 

 and PI. I, fig. 6, which is perfect in front, would lead one to infer that the umbones 

 figured by de Koninck do not exist. I have carefully examined many specimens 

 with a view of ascertaining this point, but have been unable to obtain any evidence 

 that the umbones were not terminal. I therefore for the present retain the species 

 in the genus Piinia. 



Pinna siibspatnlata, Worthen {op. supra cit.), probably belongs to M'Coy's species. 



Family AVICULID^. 



Genus Pteeonites, M'Coy (pars), 181-4. 



Pteronites, M'Coy (pars), 1844. Synops. Carb. Foss. Ireland, p. 81. 

 Xon — M'Coy, 1852. Brit. Pal. Foss., p. 391. 



Aviculopinna, MeeJc, 1867. Amer. J. Sci. and Arts, vol. xliv, p. 282. 

 — — 1872. Eep. U.S. Geol. Surv. Nebraska, p. 197. 



