DAVIDSON — I 
■SCOTTISH CAlUiONIPEROUS nUACniOPODA. 
Ill 
their internal casts, wliich arc often qnitc as instructive. In the interior of the 
dorsal valve the cardinal ])roccss is ijroporlionally largo and trilobed, under 
wliicli a median longitudinal ridge extends to a little more tiian half the length 
of the valve, and beccnnes niuch elevated and thickened towards its extremity ; 
on either side may be seen a pair of dendritic scars formed by the occlusor 
muscle ; the reniform impressions arc also well deliucd, and often much raised, 
and the surface of the valve is covered near it s margin with numerous spinulose 
asperities ; minute canals traversing the valves are also clearly visible in the 
shape of punctures, especially upon specimens that have been slightly 
weathered. 
P. loiigispimis is a common Scottish species, but which rarely attains or 
exceeds luue or ten lines in length by ten or eleven in width, ana it is quite 
certain that several so termed species have been made out of accidental dif- 
ferences peculiar to certain specimens. I have adopted the term longiqunua, 
as it stands first among the synonyms, and because I believe the species is 
best known by that denomination among British palaeontologists. P. Flcmingii 
was badly drawn and described from a very imperfect specimen ; wliile P. 
lobatits is only a variety in which the median sulcus or furrow in the ventral 
valve is deeper than usual, and is to P. longispims what P. sulcatus is to P. 
semiretic.nlutus, =, P. «/)/«o«a4- appears also to nave been drawn from a specimen 
of the shell under description, but wherein the median sinus has not been 
developed. The original figured specimens of all these so termed species were 
kindly lent to me by Prof. Fleming, and of which figures will be found in our 
plate. Some other synonyms will be recorded and explained in my larger 
work, but which cannot be alluded to in the present memoir. 
P. loiigispimis occurs in several stages. At Braidwood, in Lanarkshire, it 
occurs at three hundred and thirty-seven fathoms lower than the " EM coal 
three hundred and thirty-eight at Hallcraig; three hundred and forty-one at 
Kaes GiU ; three hundi-ed and forty-three at Langshaw ; three huucu'cd and 
fifty-four at HiU Head ; three hundi-ed and seventy-one at Kilcadzow ; and 
tliree hundred and seventy-five at Thornmuir and Mosside, all in the parish of 
Carluke. It is foimd also at KersegiU and Brockley, near Lesmahago; 
Auehentibber and Calderside, High Blautyre ; Capel Rig, East Kilbride ; the 
east bank of the Avon, near Strathavon. In Benfrewshire, at Arden- and 
Orchard-quarries, Thornliebank. In Dumbartonshire, at Castlecary. In Ayr- 
shire, at Roughwood and West Broadstone, Beith ; Auehenskeigh, Daby ; 
Goldcraig, near Kilwinning; Craigie, near Kilmarnock; and Nethernewton, 
parish of Loudon. In Stirlingshire it occurs in several stages at Craigenglen, 
Balglass Burn, Balgroehan, the Campsie main-limestone, and Corrie Bui'u. 
In iButeshire in the island of Ai'ran. In Midlothian, at Dryden, etc. In Had- 
dingtonshii'c, at East Barns, near Dumbar, etc., and is found also in Eifeshire. 
XXX. — Productus CAHBONAKiTjs. Dc Konittck. PL iv., fig. 14. 
Productus carbonarius, de Koninck, Description dcs Animaux Eossiles du 
Terrain Carbonifere de la Belgique, p. 181, pi. xii. bis, fig. 1, 1843, and 
Monographie du Genera Productus, pi. x., fig. 4. 
Of this species I am acquainted with but a single Scottish example. It 
measures ten lines in length by eleven in width. The ventral valve is 
somewhat transversely oval, gibbous and evenly rounded, with small auri- 
culate expansions, and a hinge-line as long as the greatest ^vidth of the 
shell. The external sui-face is ornamented with numerous fine thread-like 
radiating striie, tolerably regular in their course, and bifurcating but rarely 
upon their anterior prolongation. Pi-om each rib projects, at short intervals, 
numerous slender spines, the rib itself beeomiaag thic'Leued at the spot from 
