Fossils of the Niagara and Clinton Groups 57 



form, nearly of joints, as the new species above described, Tiic anuulatiom; 

 are further apart, however, and if we understand figure 10, on plate 27 of 

 the Pateontology of New York, the notches are upon the upper side of the 

 rings instead of the lower, as in this species. We have seen many columna 

 of G. ramulosus, which appeared to be perfect at their lower extremities, 

 as they were tapered down to a very small size — but have never met with 

 one still attached to the rock. We cannot therefore say how it was attached, 

 whether by a branching root or by an expanded base, as in many other 

 species. They are usually found coiled up, and the centre of the coil being 

 the small end. 



ARTICLE VI. — Fossils of the Upper Silurian Rocks, 'Niagara and Clinton 

 Groups. 



The fossils figured upon the plate opposite this page, are somewhat 

 common in the Niagara and Clinton groups, two formations which constitute 

 the most important portion of the Upper Silurian of Canada, so far as 

 palaeontology is concerned. These rocks cross the Niagara river, from the 

 State of New York into Canada, in a narrow belt, which pursues a westerly 

 course through portions of the Counties of Welland, Lincoln, and Went- 

 worth, to the City of Hamilton, and then turning to the north, stretches 

 away through Halton, Peel, Wellington and Grey, to the Georgian Bay. 

 Along this line of country a rich harvest of beautiful fossils may be collected. 

 Those upon the plate are : 



Fig. 1. — Favosites Niagarensis. 



<' 2. — Pentamerus oblongus (dorsal viev/ of a large specimen. 



•' 3. — Ditto ditto (side view of a small specimen.) 



"^ 4. — Ichthyocrinus laivis. 

 . '■'■ 5. — Strophomena depressa. 



" d.—Avicula emacerata. 



" 7 — Pliacops limulurus. 

 Fig. 7 exhibits the form of a trilobite, closely resembling Pliacops 

 caudatus, a species very common in the Silurian rocks of England, and one of 

 the most celebrated and best known fossils of this remarkable tribe in the 

 world. Our species is of an elongated oval shape, with the tail prolonged 

 into a sharp spine, and with a short rounded point in the centre of the front 

 margin of the head. There are eleven segments in the thorax, fifteen in the 

 central, and eight in each of the lateral lobes of the tail or pygidium. The 

 head is in the shape of a crescent, with the posterior angles extended back- 

 wards, and forming two sharp points. The glabella consists of one large 

 elliptical lobe in the front, and three smaller lobes behind, which are elon- 

 gated in a direction across the head, between the eyes. Each of the latera I 

 segments of the body is obtusely pointed, — bent downwards at its outer 

 extremity, and grooved upon its upper surface for a distance of two-thirds of 



