232 BRITISH CABBONIFEROUS BRACHIOPODA. 



valve becomes dilated at the sides prior to becoming elongated and transformed into 

 a cylindrical tube ; that while this singular modification was being effected the inferior 

 edge became elongated in a perpendicular direction to that of the anterior tube, but in a 

 very irregular manner, and thus producing a second tube whose sides are at the same time 

 irregular, strongly undulated, and ribbed ; that these small ribs and undulations are parti- 

 cularly observable on the portion of the tube formed by the prolongation of the cardinal 

 edge. I have never, however, had the advantage of seeing any of these singularly modified 

 specimens, and which must be of very rare occurrence ; for the generality of Belgian 

 examples that have come under my notice exactly agree as to shape with those figured by 

 Prof, de Koninck in Plate xiv of his work, as well as to those represented in the present 

 Monograph. 



Mr. Burrow found this shell in the Lower Scar Limestone of Settle, in Yorkshire, 

 while Prof, de Koninck's specimens were obtained in the equivalent Limestone of Vise, in 

 Belgium. 



Productus Deshayesianus, Be Koninck. Plate LIU, figs. 11, 12. 



Pkoductus Deshayesianus, Be Koninck. Descript. des Animaux foss. da Terr. Carb. de 



Belgique, p. 193, pi. x, fig. 7, 1843; and Mem. du genre 

 Productus, pi. xiv, fig. 4. 



Sp. Char. Shell small, semicircular about as wide as long ; hinge-line nearly straight, 

 and as wide as the greatest breadth of the shell. Ventral valve regularly arched, and 

 evenly convex ; surface marked by minute concentric ridges, from which rise closely-set 

 spiny tubercules, but which become gradually less numerous towards the margin in adult 

 individuals. Dorsal valve concave, following the curves of the ventral one. 

 Length 3, width 3^ lines. 



Obs. Two imperfect specimens only of this small species (?) have been hitherto 

 discovered in England, which, having been forwarded to Prof, de Koninck for identi- 

 fication and comparison, were declared by him to be referable to his Belgian type. Mr. 

 Burrow found his -specimens in the Low T er Scar Limestone of Settle, in Yorkshire, 

 where the shell appears to be exceedingly rare. Prof, de Koninck procured his specimens 

 from the equivalent Limestone of Vise, in Belgium. 



Productus striatus (p. 139). Plate XXXIV, figs. 1—5 ; and Plate LIII, fig. 4. 



Since describing this species, a specimen measuring nearly five inches in length by 

 rather more than the same in breadth, has been discovered by Mr. Carrington in the 

 ( urboniferous Limestone of Wctton, in Staffordshire. It has also been found in the counties 

 of Dublin, Kerry, and Leitrim, in Ireland. 



