DAVIDSON — eCO'lTISH CARBONIFEROUS BRACHIOPODA. 
181 
fig. 25 ; but of tliat I do not at present feci certain. Mr. Young has seen ex- 
amples of tliis shell from Lanarkshire, Renfrewshire, Ayrshire, and Fifeshire, 
but it is nowhere (yet discovered) so plentiful as at Corric Burn, wliere it occurs 
in a tliin bed of a white friable shale, above a coralline bed {Lifliodendron 
fasciculatuiii, Fleming, = Litlwstrotiori Marthii, M-Edw.). It is found also at 
Brockley, near Lesniahago, in Lanarkshire. 
For some time I felt uncertain whetlier the shell under description might 
not be the same as that to wliich Messrs. Norwood and Pratten had applied tlie 
name of elpcjans; but having received from Mr. Worthen and Prof, de Koninck 
several typical examples of the American sliell obtained at Chester, Illinois, I 
soon became convmeed that the Scottish species was in reality distinct. 
Messrs. Norwood and Pratten have not, however, furnished 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 tlie 
many American specimens that have come under my observation ; while, on 
the contrary, our P. Youngianus is always regularly convex and without mesial 
depression ; it is likewise mucli more regularly oval, and the sides of the beak 
do not fall perpendicularly upon the ears as in P. elegans, and, although dis- 
tinct, approaclies mostly to P. acideatus 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 Hunteriau Museum of Glasgow, who was the first to draw my 
attention to the species ; and 1 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. 
XXXVIII. — ^Prodhctus aculeatus. Martm. PI. ii., fig. 20. 
Anomites aculeatus. Martin, Petrif. Derb., p. 8, pi. xxxvii., figs. 9-10, 1809. 
Productus id., De Koninck, Monographie du Gem-e Productus, pi. xvi., 
fig. 6. 
The shells composing this species are usually nearly circular, or slightly 
longer than wide, the liinge-line being at the same time shorter than tlie 
greatest width of tlie sheU. 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, wliich is much incurved, does not overlie the hinge-line, except quite at 
its attenuated extremity. On the exterior of the valves there exists some 
irregularly scattered elongated tubercles, from wliich projected short adpressed 
spines, these tubercles being also sometimes so elongated as to produce the 
appearance of ribs ; but both Martin and Sowerby were mistaken, as was 
justly observed by Prof, de Koninck, when they stated in their descriptions of 
tlie shell that the spines "pointed backwards, or towards the beak." 
Numerons concentric unduhiting Unes 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 Stirlingshire 
it occurs in the Campsie main limestone and ii'onstone. In Lanarkshire it has 
been found at Calderside, High Blantyre. In Renfrewshire, at Orchard- 
quarry, Thoridiebank. In Ayrshire, at West Broadstonc, Beith ; Craigie, near 
KiLnai'uock ; and Auchenskeigh, Dairy. 
