186 BRITISH CARBONIFEROUS BRACHIOPODA. 



Chonetes Hardrensis, Phillips. PI. XLVII, figs. 12—16, 17, 18, and 25? 



Pecten - - - - Ure. Hist, of Piiitherglen and East Kilbride, p. 317, pi. xvi, 



figs. 10, 11, 1793. 

 Chonetes Hardrensis, Phillips. Figures and Descriptions of the Palaeozoic Fossils 



of Cornwall and West Somerset, p. 138, pi. lx, fig. 104, 



1841. 

 Lept(ENa (Chonetes) Hardrensis, M'Coy. British Pal. Foss., 454, 1855. 

 Chonetes Hardrensis, Bar. Mon. of Scottish Carb. Brach., pi. ii, fig. 2, 1861. 



Spec. Char. Shell marginally semicircular, wider than long, concavo-convex ; hinge- 

 line straight, and either a little shorter or somewhat longer than the width of the shell, 

 with rounded or angular terminations ; each valve is provided with a sub-parallel area, but 

 which is widest in the ventral one, and divided in the middle by a small fissure, partially 

 covered by a pseudo-deltidium ; ventral valve moderately convex, sometimes slightly 

 depressed along the middle and flattened towards its auriculate cardinal extremities : 

 the beak, which is small and incurved, does not overlie the hinge-line, while the dorsal 

 valve assumes in different specimens a greater or lesser degree of concavity, with, at times, 

 a slight longitudinal elevation along the middle, and flatness near the cardinal extremities. 

 The surface of both valves is covered with numerous thread-like, radiating, and often 

 bifurcating striae, which increase in number by the interpolation of striae at various 

 distances from the beak and umbo, so that as many as 120 striae may in some 

 examples be counted round the margin, while at irregular distances small spines 

 rise from their rounded surface in addition to those on each side of the beak ; in 

 adult examples there exist along the cardinal edge from five to nine slanting, tubular 

 spines, which become longer and larger as they approach the extremities of the cardinal 

 edge. The valves are articulated by means of teeth and sockets, while the muscular 

 and other impressions do not differ materially from those already described in the 

 preceding species. Dimensions variable ; an average-sized specimen has measured — 

 length 7, width 11, greatest depth 1^ lines. 



Obs. The determination of the present species has given me much trouble ; and 

 although I have spent much time in the endeavour to arrive at a satisfactory conclusion, it 

 is not without some hesitation that the term Hardrensis is here provisionally retained ; 

 provisionally, because I am as yet unable to determine whether Phillips's Devonian shell 

 is the same as that to which Schlotheim, in 1820, applied the denomination sarcinulata, 

 as Prof, de Koninck's illustrations of this last differ so much from those given by 

 Prof. Schnur and some other palaeontologists. I am likewise uncertain whether J. de 

 C. Sowerby's Lept. sordida (1840) be really a synonym of the last-named shell, or 

 different from Phillips's Hardrensis, as has been stated to have been the case by some 

 authors ; and lastly, because my learned friend, Prof, de Koninck, who has paid so much 



