REFERENCE 

 LIBRARY. 



PRODUCTUS. 1 71 



1861. PBODFCTUS SCABBICULUS, Davidson. Brit. Foss. Bracb., vol. ii, pt. 5, 



p. 169, pi. xliii, figs. 58. 

 Ibid., vol. iii, p. 103, pi. xx, figs. 

 3(?),4-6. 



Description. Ventral valve convex, gibbose, transverse or occasionally slightly 

 elongate. Umbo flattened, moderately elevated, recurved over the hinge-line. 

 Sinus low, broad, undefined. Surface marked on the umbo and wings with coarse 

 concentric ridges, which vanish in front ; and also covered by about fifty coarse, 

 close, rounded, irregularly alternating and occasionally discontinuous ribs, 

 occasionally carrying spines (which in some specimens appear to be set forward 

 and in others backwards). Wings with a few large spines in their corners. 



Dorsal valve strongly geniculated, marked on the flat portion with coarse, 

 rounded, divaricating ribs, which are crossed and nodulated by closer concentric 

 ridges ; these ribs alone being continued over the elbow, in front of which they 

 are very irregular. 



Size. About 28 mm. long by 34 mm. wide. 



Localities. In the Woodwardian Museum is a ventral valve from Croyde and 

 two dorsal valves. In the Porter Collection is a ventral valve from Smoking 

 House Lane, and two from Pilton, and eight dorsal valves from Pilton, Roborough, 

 and Poleshill. 



Remarks. I have been unable to recognise the Devonshire examples which 

 Phillips and Davidson figured. Their figures of the dorsal valves with their 

 corded ornament and internal markings are clear. Phillips's figure of the ventral 

 valve is certainly very vague in itself, but in conjunction with his description it 

 may be taken to represent a small specimen of this species. Davidson's figure is 

 covered with spines, and it appears very difficult indeed to distinguish it from 

 some of the figures which he gives of Strophalosia productoides, while in a slab in 

 the Davidson Collection labelled by him " St. productoides and P. scabriculus" I 

 have been able to discover only specimens of the former species. 



At the same time some ventral valves have been found, which, though 

 generally distorted, appear to present all the characters of this species. Having 

 compared them with numerous Carboniferous specimens, and especially with those 

 in the Bristol Museum, to which Phillips himself likened his Pilton specimens, I 

 see no reason for hesitating to refer them to this Carboniferous form. These 



o 



specimens correspond, moreover, with a number of dorsal valves from the Pilton 

 beds, of some of which there can be no doubt that they belong to P. scabriculus, 

 though it is difficult to be certain whether others can be distinguished from 

 Sir. productoides. 



