148 BRITISH CARBONIFEROUS BRACHIOPODA. 



Productus cora, D 'Orhigny. PL XXXVI, fig. 4, and PI. XLII, fig. 9. 



Productus cora, B Orb. Paleontologie du Voyage dans l'Amerique Meridionak, 

 pi. v, fig. 8, 9, and 10, 1842. 



— comoides, Be Koninck. Descrip. des Anim. Fossiles du Terrain Carb. de 



la Belgique.pl. xi,fig. 2'"' t, and fig. 5"- 6 - (not of Sow.), 1843. 



— corrugata, M'Coy. Synopsis of the Carb. Limest. Fossils of Ireland. 



pi. xxvi, fig. 13, 1844. 



— Neitedievi, Be Verneuil. Eussia and the Oural Mountains, vol. ii, 



pi. xviii, fig. 11, 1845. 



— coitA. Be Koninck. Monographic du genre Productus. pi. iv, fig. 4, and 



pi. v, fig. 2, 1847. 



— corrugata. M'Coy. British Pal. Foss., p. 459, 1855. 



— piriformis, M'Chesney. Desc. of New Species of Fossils from the 



Palaeozoic Rocks of the Western States of America, p. 40, 

 1859. 



— cora, Bav. Mon. of Scottish Carb. Bracli., pi. iv, fig. 13, 1860. 



Spec. Char. Shell thin, longitudinally oval, or semi-cylindrical, usually longer than 

 wide ; hinge-line about as long as the breadth of the shell; ventral valve gibbons, evenly 

 convex, or slightly flattened along the middle : beak wide and incurved ; ears small, 

 and generally crossed by four or five deep undulating folds or large wrinkles, which 

 extend to some distance over the lateral portions of the valves. Surface covered with 

 numerous longitudinal, straight or slightly flexuous, narrow, thread-like, rounded stria 1 , with 

 sulci or interspaces of rather less width, while smaller striae are often intercallated between 

 the larger ones, the ribs being also regularly crossed by small concentric lines. Spines 

 few in number, sparingly scattered over the surface, but more numerous on the cars. 

 Dorsal valve concave, following the curves of the opposite one, and similarly ornamented. 



Dimensions variable, some examples have attained or exceeded two and a half inches in 

 length, by three and a half in width. 



Obx. This Productus is well characterised and distinguishable from its congeners 

 both by shape and sculpture ; but the four or five large concentric wrinkles which usually 

 cover the ears and lateral portions of the valves are much less developed in certain 

 examples than in others. In the dorsal valve, the visceral portion of some specimens is 

 also entirely crossed by a variable number of concentric folds or wrinkles (as represented in 

 PI. XLII, fig. 9), but which do not exist in the generality of specimens. The shell varies 

 likewise very much in shape, being at times almost oval, while in other examples the 

 margin becomes considerably expanded. Prof, de Koninck, who has had the advantage of 

 being able to examine D'Orbigny's original specimens, positively asserts that they cannot 

 be distinguished from the European examples we are now describing, and that consequently 

 Prof. M'Coy's P. corrugata will require to be added to the synonyms ; and I believe that 

 my Belgian friend is likewise correct when he refers the Russian P. JYrffcJirri to 

 D'Orbigny's species. 



