174 



Horizon and Locality. In Assise E 3 e and /, Upper Etcheminian, 

 at Dugald brook. Frequent. 



The following are measurements of the valves of this species : 



Dimensions. E. 3 e, left valve, length 2 mm., width 2J mm., depth $ mm. 



E. 3 e, " " 2 mm., " If mm., " \ mm. 

 E. 3 e, right " " 2 mm., " 2 mm., " mm. 

 E. 3 /, " " " 2J mm., " 2 mm., " mm. 



This species, by its smooth surface and pointed form, recalls the genus 

 Beyrichona of the Protolenus Fauna ; but it has not the broad flattened 

 area, near the hinge which marks that genus: on the contrary it is there 

 most prominent ; this feature belongs to the genus Schmidtella. 



" From S. pervetus this species is distinguished by its finer ornamenta- 

 tion and pointed lower margin ; and from S. cambrica of the Protolenus 

 fauna by its smoother surface and narrow fold at the cardinal line. No 

 Silurian Schmidtella has the pointed valve of this species." 



" HOLASAPHUS, PI X., figs. 3a to c. 



Trans. Roy. Soc. Can., 2nd ser., vol. 1, p. 268. 



Holasaphus. " Among the fossils from Young point was a trilobite apparently 

 other genera, related to Asaphus, but different from any described genus. From Bathy- 

 uruft, Bill., it is excluded by the shallowness of the furrows on the head- 

 shield, and the low relief of the glabella ; it is shut out of Bathyurellus, 

 Bill., by the narrow marginal fold and long axis of the pygidium ; from 

 Protypus, Wale., by its shorter glabella, inclined to conical, and the pro- 

 longed angles of the free cheeks ; from Asaphiscus, Meek, by its Mega- 

 laspis-like pygidium ; from Asaphelina, Mun-Cham. and J. Berg., by 

 having only one spine to the pygidium ; from Platypeltis, Call., by its 

 shorter, cylindro-conical glabella, and markedly segmented and lobed pygi- 

 dium. 



" HOLASAPHUS CENTROPYGE, PI. IT., figs. 4a and b. 



Holasaphus " Middle piece of the head sub-quadrate. Anterior margin with a dis- 

 tinct fold. Glabella sub-cylindrical, rounded in front, about one-quarter 

 longer than wide, not furrowed. Occipital ring narrow, divided from the 

 glabella by a narrow fold, and having an obscure tubercle at the back on 

 the median line. Fixed cheeks slightly wider at the middle than half of 

 the width of the glabella, widening before and behind the eyelobe, meet- 

 ing in front of the glabella, furnished with short, prominent eyelobe?, no 

 ocular fillet. Posterior furrow and fold narrow, the former shallow. 



