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BRITISH DEVONIAN BRACHIOPODA. 



April, 1840, under the denomination of Orthis productoides, and on the 30th of May of 

 the same year, by Sowerby, as Leptcena caper ata. It has also received several other 

 designations j to imperfectly preserved flattened casts showing only the zigzag concentric 

 markings Phillips applied the denomination memiranacea, and one of De Koninck's 

 figures of P. Murchisonianus undoubtedly belongs to the species under description. It is 

 not an Orthis, nor can it be classed under Leptcena, but was, in 1846, correctly located 

 by Prof. King in his genus or sub-genus Sfrop/ia/osia, 1 but I hardly consider the last- 

 named author equally fortunate while placing Prod, subaculeatus in the same sub-genus. 

 Sir R. Murchison states that he gave the name Orthis productoides to this shell because, 

 in his opinion, it appeared to establish a passage from Orthis to Productus and Leptcena, 

 but at that period the sub-genus Strophalosia had not been established. Prof, de Koninck 

 thinks Sir R. Murchison right when considering the species under description to be 

 situated on the limits of the genera Productus and Chonetes, and the learned Belgian 

 palajontologist places the shell in the genus Productus. He also states to have been mis- 

 taken when he united St. productoides with Sowerby's P. spiuulosus, but from which it is 

 at once distinguished by its well-marked double area, a character never seen in the Car- 

 boniferous P. spinidosus. M. de Koninck observes, moreover, relative to the surface of 

 the dorsal valve, that it is marked with irregular concentric wrinkles, similar to those of 

 the opposite valve, but generally more lamellar ; that the spines are more often wanting, 

 and are replaced by small pits corresponding to the tubercles or spines of the opposite 

 one. None of the specimens I have been able to procure showed spines in this valve, and 

 I therefore mention their existence solely on the authority of Prof. L. de Koninck, for they 

 are seen only on the dorsal valve of those specimens of his P. Murchisonianus which do 

 not, I consider, belong to the species under description. 1 am at a loss to understand 

 why some palaeontologists should have considered it difficult to distinguish this shell from 

 Productus subaculeatus, for they appear to me perfectly distinct, as a reference to figures 

 will easily explain. Prof. M'Coy states that all the specimens which he has examined 

 of the species, named by Sowerby himself, were certainly specifically identical with 

 L. membranacea of Phillips, and that it is only the dorsal valve of typical examples of that 

 species that are nearly flat ; that the species varies greatly in the proportional strength of 

 the two kinds or ornaments, and when the beautiful concentric zigzag wrinkling is very 

 strongly marked, the elongated tubercles can scarcely be seen ; and that, on the other 

 hand, when the quincuncial spine-tubercles are strongly marked, the transverse wrinkling 

 cannot be so distinctly seen ; and that this has perhaps given rise to the two species dis- 

 tinguished by Mr. Phillips, although, from examination of Sowerby's types and numerous 

 specimens on the spot when they were first, found, and where they abound, he readily 

 traced every gradation between the supposed different types ; lastly that none of the pub- 

 lished figures do justice to the singular beauty and regularity of the minute, transverse 

 wrinkling. 



1 Annals and Mag. of Nat. Hist., vol. xviii, July and August, 18-16. 



