DAVIDSON — SCOTTISH CARBONIFEEOUS BRACHIOPODA. 



Ill 



their internal casts, which are often quite as instructive. In the interior of the 

 dorsal valve the cardinal process is proportionally large and trilobed, under 

 which a median longitudinal ridge extends to a little more than half the length 

 of the valve, and becomes much 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 are also well defined, and often much raised, 

 and tlie surface of the valve is covered near its 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. longiHpi?ius is a common Scottish species, but which rarely attains or 

 exceeds nine or ten lines in length by ten or eleven in width, and 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 lo7igispmus, 

 as it stands first among the synonyms, and because I believe the species is 

 best known by that denomination among British palaeontologists. P. Flemingii 

 was badly drawn and described from a very imperfect specimen ; while P. 

 lohatus is only a variety in which the median sulcus or furrow in the ventral 

 valve is deeper than usual, and is to P. longispimis what P. sidcatus is to P. 

 semireticulatus, =, P. spinoma appears also to have 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. Eleming, 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. longispimis occurs in several stages. At Braidwood, in Lanarkshire, it 

 occurs at three hundred and thirty-seven fathoms lower than the " Ell coal 

 three liundred and thirty-eight at Hallcraig ; three hundi'ed and forty-one at 

 Haes Gill ; three hundi-ed and forty -three at Langshaw ; three hundred and 

 fifty-four at Hill Head; three hundred and seventy-one at Kilcadzow; and 

 three hundred and seventy-five at Thornmuir and Mosside, all in the parish of 

 Carluke. It is found also at Kersegill and Brockley, near Lesmahago; 

 Auchentibber and Calderside, High Blantyre ; Capel Rig, East Kilbride ; the 

 east bank of the Avon, near Strathavon. In llenfi-ewshire, at Arden- and 

 Orchard- quarries, Thornliebank. In Dumbartonshire, at Castlecary. In Ayr- 

 shire, at iioughwood and West Broadstone, Beith ; Auchenskeigh, Daby ; 

 Goldcraig, near Kilwiiming; Craigie, near Kilmarnock; and Nethernewton, 

 parish of Loudon. In Stii'lingshire it occurs in several stages at Craigenglen, 

 Balglass Burn, Balgrochan, the Campsie main-limestone, and Corrie Burn. 

 In Buteshire in the island of Arran. In Midlothian, at Dryden, etc. In Had- 

 dingtonshire, at East Barns, near Dumbar, etc., and is found also in Eifeshii'e. 



XXX. — PiiODUCTus CARBONAEius. Dc Koniuck. PI. iv., fig. 14. 



Prodiidus carbonarizis, de Koninck, Description dcs Animaux Eossiles du 

 Terrain Carbonifere de la Belgique, p. 181, pi. xii. bis, fig. I, 1843, and 

 Monographic du Genera Productus, pi. x., fig. 4. 



Of this species I am acquainted with but a single Scottish example. It 

 measm-es ten lines in length by eleven m 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 width of the 

 shell. The external surface is ornamented with numerous fine thread-like 

 radiating striee, tolerably regular in their course, and bifurcating but rarely 

 upon their anterior prolongation. Erom each rib projects, at short intervals, 

 numerous slender spines, the rib itself becoming thickened at the spot from 



