Vol. 69.] OF THE COMLEY BRECCIA-BED. 39 



Facial suture. — Slightly convergent in front of the eye, more 

 strongly divergent behind it. 



Test. — The external casts invariably show a granular surface; 

 but, as this varies in agreement with the coarseness or fineness of 

 the matrix, it is probable that the external surface of the cranidium 

 was smooth. 



This form has many points in common with Plychoparia (Lio- 

 stracus) pulchella from the Davidis Fauna at Comley. It differs, 

 however, in the greater width of the glabella, the concurrent 

 narrowness of the fixed cheeks, the absence of the ocular ridge, 

 and in the shorter and more erect occipital spine. Also the eye- 

 lobe appears to be somewhat larger and situated rather more 

 forward. 



Through the above-mentioned species, Pt. (L.J lata is related to 

 Pt. (L.) valida Matthew and Pt. (L.) linnarssoni Brogger. 



Ptychopakia (L.) ? dubia Cobbold. (PI. Ill, figs. 19 a & 19 b.) 



Q. J. G. S. vol. lxvii (1911) p. 295 & pi. xxv, figs. 19-21. 



Two small cranidia from the Breccia-Bed agree with this species, 

 so far as they go. It is obviously quite possible, however, that 

 they are immature individuals of the form Pt. (L.) lata. 



IV. The Stratigraphical Horizon of the Breccia-Bed. 



So many of the trilobites are either indifferently preserved, or 

 belong to species hitherto undescribed, that any correlation of the 

 Breccia-Bed with a well-defined Cambrian horizon elsewhere must 

 be somewhat hypothetical. 



The two Welsh species, Oonocoryphe bufo Hicks and Microdiscus 

 punctatus Salter, are quoted from the Menevian of St. David's, the 

 former from the grey beds at the base of the group. 1 



M. punctatus is also found in Scandinavia, but was described by 

 Linnarsson under the two names M. scanicus and M. eucentrus? 

 Both at Andrarum 3 and at Bornholm i it occurs in the P.-tessini 

 Zone, and also, at the latter locality, in the P.-davidis Zone. 



Conocoryphe cequalis Linnarsson marks a definite sub-zone near 

 the top of the Scandinavian P.-tessini Beds, while C. impressa 

 Linnarsson occurs in the lowest sub-zone of the same group. The 

 two species are found at Andrarum (Moberg, op. cit.) and at Born- 

 holm (Gronwall, op. cit. pp. 92, 101, & 168) in the same relative 

 positions. 



1 J. W. Salter & H. Hicks, Q. J. G. S. vol. xxv (1869) p. 53. 



2 P. Lake, ' Brit. Camb. Trilob.' Monogr. Palseont. Soc. vol. Ixi (1907) pt. 2, 

 p. 36. 



3 J. C. Moberg, Geol. Foren. Stockholm Forhandl. vol. xxxii (1910) pt, 1, 

 pp. 57-59. 



4 K. A. Gronwall, Danmarks Geol. Undersog. ser. 2, No. 13 (1902) pp. 79-S1 

 & 167. 



