142 ME. F. E. COWPEE EEED 01* THE FATTSTA OF IHE [May I909, 



must be regarded as of especial importance, and the evidence of 

 the fatinistic relations and the probable stratigraphical equivalence 

 of these Irish beds with parts of the Scandinavian and Prussian 

 Orthoceras- and Cystidean Limestones may again be emphasized. 



(2) "With regard to the fauna of the ashy grits (Shangort 

 Beds) the specimens are mostly in such miserable preservation that 

 tbe specific identification or even the affinities of the fossils are as a 

 rule uncertain. However, the few which can be more satisfactorily 

 determined indicate that there exists a certain, though not strong, 

 difference between this fauna and that of the limestones ; but this 

 may be more apparent and accidental than real. We do not fail to 

 note that the important genus Pliomera still persists, and indeed is 

 represented by more than one species, proving that we are still 

 dealing with Lower Bala beds. Porambonites also appears to occur. 

 The possible presence of a member of the subgenus C7iasmops 

 suggests a somewhat higher palseontoiogical horizon than that of the 

 limestone, but there is nothing definite to show that the ashy grits 

 are far removed in age from the latter. The different nature of the 

 matrix shows the existence of different physical conditions during 

 their accumulation, and therefore the change in the composition of 

 the fauna may be partly due to the new environment, and the occur- 

 rence of a somewhat different assemblage of organisms may be thus 

 accounted for. The fact that blocks of the fossiliferous limestone 

 are found in the ashy grits is evidence that some time must have 

 elapsed after the limestone was formed ; but that they belong to 

 the same period seems conclusively proved, palaeontologically, by the 

 presence of members of the genera Pliomera and Porambonites, and 

 by the absence of a later or Middle Bala fauna. 



The Tramore Limestones, with which the faunas of the Tourma- 

 keady and Shangort Beds may be best compared, lie below the 

 Ccenograptus-Sh&les, that is, below equivalents of the Glenkiln 

 Shales, and it was suggested by me in 1899 that their lower 

 portion corresponded with part of the OtfAoceras-Limestone 

 ( = Arenig) of the Baltic region. It does not, however, seem 

 necessary to regard them as of Arenig age, because, as Dr. Marr 

 has pointed out, the migration of faunas in Ordovician times was 

 westward, so that the older faunas of Sweden appear on slightly 

 higher horizons in the British Isles. Moreover, the typical fauna 

 of the British Arenig is absent. W T e may, therefore, look upon the 

 Tounnakeady and Shangort Beds as probably of Lower Llandeilo 

 rather than of Arenig age. 



B. Description of New Species. 



IliiENES WEAVEEI, SO. nOV. (PI. VI, figs. 1 rt-1 C, 2, & 3.) 



Description: — Head-shield slightly convex from side to side, 

 with free cheeks arching steeply down on each side and the middle 

 shield flattened ; strongly and rather suddenly bent down in front, 

 nearly at right angles, at about one-third of its length (that is, 



