DAVIDSON SCOTTISH CARBONIFEROUS BRACHIOPODA. 



181 



I \<y. 25 ; but of tliat I do not at present feel certain. Mr. Young lias seen ex- 

 amples of tliis shell from Lanarkshire, Renfrewshire, Ayrshire, and Fifeshire, 

 jut it is nowhere (yet discovered) so plentiful as at Corrie Burn, where it occurs 

 in a thin bed of a white friable shale, above a coralline bed {Litlwdemlron 

 fasciculatum, Fleming, = LitJwstrotion Martini, M-Edw.). It is found also at 

 Brockley, near Lesmahago, in Lanarkshire. 



For some time I felt uncertain whether the shell under description might 

 not be the same as that to which Messrs. Norwood and Pratten had applied the 

 name of elegans ; but having received from Mr. Worthen and Prof, de Koninck 

 several typical examples of the American shell obtained at Chester, Illinois, I 

 ^ioon became convinced that the Scottish species was in reality distinct. 

 Messrs. Norwood and Pratten have not, however, fui'uished us with a charac- 

 teristic representation of their species, which is not evenly convex, but longitu- 

 dinally flattened, and even sometimes depressed along the ventral valve in the 

 many American specimens that have come under my observation ; wliile, on 

 the contrary, our P. Yoiingianus is always regularly convex and without mesial 

 depression ; it is likewise much more regularly oval, and the sides of the beak 

 do not faU perpendicularly iipon the ears as in P. elegans, and, although dis- 

 tinct, approaches mostly to P. aculeatus of Martin. Mr. Salter assures me 

 that there are none of Prof. Hall's figures in the Iowa report at all like our 

 Scottish shell. I have, therefore, ventured to name the shell after Mr. J. 

 ■Young, of the Hunterian Museum of Glasgow, who was the first to draw my 

 attention to the species ; and I am indebted to Mr. Salter for the loan of a 

 specimen from the carboniferous limestone of LlangoUen, in Wales, which may 

 be seen in the Museum of Practical Geology. 



XXXYIII. — PnoDucTTJs ACULEATUS. Martin. PI. ii., fig. 20. 



\nomites aculeatus. Martin, Petrif. Derb., p. 8, pi. xxxvii., figs. 9-10, 1809. 

 Productus id., De Koninck, Monographic du Genre Productus, pi. xvi., 

 fig. 6. 



The shells composing this species are usually nearly circular, or slightly 

 longer than wide, the hinge-line being at the same time shorter than the 

 greatest width of the shell. The ventral valve is evenly convex, and without 

 sinus, while the dorsal one is very concave, closely following the curves of the 

 opposite valve. The ears are very thin and small, usually broken ; the beak 

 also, which is much incurved, does not overlie the hinge-line, except quite at 

 ':s attenuated extremity. On the exterior of the valves there exists some 

 UTegularly scattered elongated tubercles, from which projected short adpressed 

 spines, these tubercles being also sometimes so elongated as to produce the 

 appearance of ribs ; but both Martui and Sowerby were mistaken, as was 

 justly observed by Prof, de Koninck, when they stated in their descriptions of 

 the shell that the spines "pointed backwards, or towards the beak." 

 Numerous concentric undulating lines of growth may also be detected on 

 either valve. The interiors of the valves have not been hitherto discovered ; 

 and although the species does not appear to have ever attained large dimensions, 

 those known to me from Scotland did not exceed some five lines in length by 

 four and a-half in width. 



In Scotland the shell has been found in several localities. In Stirlino:shire 

 it occurs in the Campsie main limestone and ironstone. In Lanarkshire it has 

 been found at Calderside, High Blantyre. In Renfrewshire, at Orchard- 

 quarry, Thornliebank. In Ayrshire, at West Broadstone, Beitli \ Craigie, near 

 Kilmarnock ; and Auclienskeigh, Dairy. 



