part 4] Cambrian horizons of comley. 345 



two varieties may be readily compared, the scale of enlargement 

 used in fig. 2 is half of that used in fig. 1 (p. 343). 



The exterior is often beautifully preserved, ' the fine radiating 

 striae that are sometimes raised lines ' l are particularly well marked 

 (PI. XXII, fig. 5). 



Locality and horizon. — Comley. Lower Cambrian, from the 

 Streniiella Limestone, horizon Ac 4 . 



Obolella (?) grqomii Matley. (PL XXI, fig. 27.) 



Obolella (?) groomii Matley, 1902, Q.J.G.S. vol. Iviii, p. 137 & text-figs. 1-2. 

 Obolella groomii Matley, Walcott, 1912, U.S. Geol. Surv. Monogr. vol. li, p. 595 

 & text-figs. 52 a-52 b. 



Several examples of this species have been found in the mottled 

 and greenish-grey beds at the base of the Lower Comley Sandstone, 

 at the Road Quarry in the Cwms. Fragments are readily identi- 

 fied by the external characters, the edges of successive lines of 

 growth being very sharp, and almost ' undercut ' in their sculpture. 

 The shell-substance is well preserved in the sandstone, and appears 

 to be corneous. It is doubtful whether it was ever to any con- 

 siderable extent composed of carbonate of lime, for the shells are 

 not preserved • as empty casts notwithstanding the open, sandy 

 nature of the rock. 



As with the Malvern specimens, dorsal and ventral valves can- 

 not be distinguished with any certainty, and no interiors have been 

 met with. In view of these facts the generic reference must 

 remain doubtful. 



Locality and horizon. — Comley, the Cwms sub-area; Lower 

 Cambrian, horizon Ab r 



ACROTRETID^ Schuchert. 



Acrothele Linnarsson. 



Acbothele COBIACEA Linnarsson. (PI. XXIII, figs. 19 rt-22 b.) 



Acrothele coriacea Linnarsson, 1876, Biliang K. Svenska Vetensk.-Akad. Handl. 



vol. iii, No. 12, p. 21 & pi. iv, figs. 44-48. 

 Acrothele of. granulata Linnarsson, Matley, 1911, Q. J. G. S. vol. lxvii, p. 302 



& pi. xxvi, figs. 9 a-9 b. 

 Acrothele coriacea Linnarsson, Walcott, 1912, U.S. Geol. Surv. Monogr. vol. li, 



p. 642 &pl. lvi, figs. 1, 1 a-li. 



The specimens submitted to Dr. C. A. Matley were not wholly 

 satisfactory ; he noticed, however, that the position of the apex of 

 the ventral valve was more in accord with that of A. coriacea than 

 with that of A. (JRedlicliella) granidata. Since his notes were 

 written, Dr. C. D. Walcott's work has appeared, with details as to 

 the aspect of the granulations of both species. 



A number of additional specimens have now come to light from 

 the JBillingsella Bed of Caradoc Dingle, and these agree in all 

 respects with the published descriptions of A. coriacea. The shells 

 usually split along one of the inner layers, which are bright and 

 glistening. The exterior surface of the ventral valve near the 



1 C. D. Walcott, 1912, p. 589. 



