44 Proceedings of the Royal Physieal Society. 



Conchia; pilosce* He says it is covered with " small spines 

 resembling hair, and so numerous that a large example 

 contains upwards of 10,000." The detached spines of the 

 larger forms of Productus were probably the objects on which 

 the genus Arhiisculites was founded by Dr P. Murray, 

 described as " very delicate vermiform bodies, in fragments 

 of different lengths, shining with metallic lustre, neither 

 articulated nor cellular, and resembling broken bits of silver 

 wh'e." f 



The British Carboniferous Bivalves {Zamellihranehiatcc, 

 Pelyeipoda, or Conchifera as they are sometimes called) have 

 not been studied to anything like the extent the Brachiopoda 

 have. A sufficiently disinterested worker like Mr Davidson 

 has yet to come forward, and undertake the elucidation of 

 this important and difficult class. In the specific determina- 

 tion of these shells we are dependent almost solely on two or 

 three works. Phillips' " Illustrations of the Geology of York- 

 shire," X M'Coy's " British Palseozoic Fossils," § and the 

 " Synopsis of the Carboniferous Limestone Fossils of Ire- 

 land," II by the same author. The first of these works may 

 be said to be practically obsolete, the third is in sad need of 

 revision and correction; whilst the second, extremely good 

 so far as it goes, does not encompass the subject sufficiently 

 for the practical purposes of the Palccontologist. Not only 

 are individual works on our Carboniferous Bivalve Shells 

 wanting, but even papers and memoirs in the publications of 

 scientific societies are of the most meagre description. In 

 fact, this branch of the Palaeozoic Mollusca generally is in a 

 similar state of chaos to the Brachiopoda, when their study 

 was first undertaken by Mr Davidson. There is really more 

 good work to be done amongst these shells and the Uni- 

 valves than in any other group of fossil organic remains 

 known to us. 



* History of Paitherglen, etc., p. 316, t, 15, f. 7. 



t "Account of the Arhusculitcs argcntca from the Carboniferous Limestone 

 of Inverteil, near to Kirkcakly in Fifeshire " (Edin, N. Phil. Jour., 1831, 

 xi., p. 147). 



X Pt. 2. The Mountain Limestone District, 4to, London, 1836, 



§ Fasciculus 3, 4to, Cambridge, 1853. || 4to, Dublin, 1844. 



