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BRITISH DEVONIAN BRACHIOPODA. 



Productus pr^longus, Sow. (sp.). PI. XIX, figs. 22 — 25. 



Lepmna piuclonga, Sow. Trans. Geol. Soc, vol. v, tab. liii, fig. 29, May 30, 1840- 

 Phoducta — WCoy. British Pal. Foss., p. 390, 1852. 



Spec Char. Shell known only in the state of casts of an elongated oval or sub- 

 cylindrical shape ; hinge-line usually not quite so long as the width of the shell. 

 Ventral valve gibbous, with depressed rectangular ears ; beak incurved. Surface 

 longitudinally divided by a slight median depression, or small ridge, from which rise at 

 variable intervals four or five long spines. The surface, in the casts, is even as well as 

 irregularly and finely striated. Dorsal valve concave, following the curves of the opposite 

 one, and similarly marked. A few concentric wrinkles exist also on the ears and lateral 

 portions of the beaks. Proportions variable — 



Length 1 inch 3 lines, width 1 inch 2 lines. 



Obs. It is not always possible to describe completely a shell of which we possess only 

 imperfect casts and impressions. Still they are so exceedingly abundant in the brown grits 

 and grey shales of the Marwood and Pilton beds of North Devon and West Somerset, 

 that it becomes one of its most important species. It is there likewise associated with 

 Strophalosia productoides, which appear to be equally abundant. Professor M'Coy 

 observes, at p. 390 of his work on British Palaeozoic fossils, that he "was greatly 

 surprised to find, on examining the unique specimens of this species in the Cambridge 

 collection, originally figured and described by Sowerby, that the impression of the ventral 

 valve (not figured) shows a strong, narrow, rounded mesial ridge of exactly the size and 

 shape of that in P. mesolobus (a very slight indication of which may be now recognised in 

 a notch in the lower margin of Sowerby's end view) ; and further, that along the corre- 

 sponding line on the middle of the dorsal valve, there was a narrow, rough, abraded space, 

 from which there could be no doubt the narrow ridge had been either broken in 

 extracting the specimen from the matrix, or had been worn off from the soft sandstone 

 in the carriage." The distinctness (he adds) of the mesial fold in the mould of the ventral 

 valve would cause the specimens to be referred to P. mesoloba, were it not for the distinct 

 longitudinal striation ; and as this is also the distinguishing character of P. Ckristiani 

 of de Koninck, he has little doubt of the identity of the species, allowance being made for 

 difference in size, and the spines being rather more numerous than in the example figured 

 by Koninck. I cannot, however, upon such imperfect material, identify with any degree 



. P. subaculeatas is one of the most far-spread fossils of the northern hemisphere ; we know it 

 in Russia, from the Government of Novogoiod, as far as the Rivers Wol and Uchta, affluents of the 

 Petchora, on the north, and as far as Voroneje, on the south ; we also possess a specimen from the 

 Altai. Everywhere in Russia, as well as in Belgium, in France, and in England, this species is 

 Devonian." 



