28 MR. E. S. COBBOLD OX THE TRILOBITE EATJXA [March. 1913,. 



of green sandstone of much finer grain or of limestone containing 

 fossils of the Protolenus-Callavia Fauna. 



In most cases these fossils belong to the Bellimarginatus group 

 of that fauna, although sometimes they may belong to the Helena 

 group. 1 



At a point near Comley Brook, 2 within 300 yards of the Quarry 

 Ridge, the Breccia-Bed, the trilobites of which are described in the 

 present paper, rests upon solid and regularly-bedded green sand- 

 stones of the Lower Cambrian. 



The breccia is composed of blocks and chips of green sand- 

 tone (both fossiliferous and barren) and of pinkish limestone, the- 

 fossils including many of the species of the ' Helena group ' of the 

 Protolenus-Callavia Fauna, and, apparently, of no other group. 

 The matrix of this breccia consists of comminuted fragments of 

 the same materials, and has consolidated to a green sandstone of 

 very much the same aspect as the parent rock. This matrix varies- 

 a little from point to point in the bed, in places becoming some- 

 what coarser and having some admixture of quartz-grains, in other- 

 places becoming more calcareous and sometimes fine-grained. 



It is from this matrix that the new Paradoxides fauna has 

 been collected. 



Fortunately, before the Breccia-Bed was opened up, many fossils 

 of the Helena group, embedded in a band of the Lower Cambrian 

 green sandstones, had been found at Excavation No. 47 in the bed 

 of Comley Brook, 3 and it is abundantly evident that the breccia is 

 largely made up of fragments of these fossiliferous green sand- 

 stones. 



Previously, the fossils of the Helena group had been found 

 only in the well-known red Olenellus Limestone of Comley Quarry - r 

 now they have been found in the green sandstone, which forms the 

 main body of the Lower Cambrian of the district, but there is 

 no evidence available at present indicating to what depth below 

 the Olenellus Limestone they descend. 



The thickness of the Breccia-Bed is about 5 feet ; it rests 

 immediately upon the well-bedded Lower Comley green sandstone,, 

 without any sign of faulting along the surface of junction ; its 

 upper limit, however, is probably a faulted one. It is succeeded 

 above by brownish shale, which apparently belongs to another 

 horizon of the Middle Cambrian. 



III. Description of the Trilobites. 

 Paradoxides Brongniart. 



The matrix of the Breccia-Bed is plentifully charged with 

 fragments of Paradoxides, which indicate an undescribed form,, 

 possessing characters in common with several well-known species. 



1 E. S. Cobbold, Q. J. G. S. vol. lxvii (1911) pp. 297, 298. 



- Rep. Brit, Assoc. 1912 (Dundee) (in the press), Excavation No. 49. 



3 Ibid. 



