Fossils of the Lowe?' Silurian Roclcs oj Canada. 47 



an elongated oval form, tapering gradually from the head to the tail. The 

 thorax consists of thirteen segments, each one of which is flattened to a 

 sharp edge on the anterior side, near its extremity, and slightly curved 

 forward, as in Isotelus gigas. In perfect specimens, the central lobe of the 

 body is much elevated, and forms a strong, rounded serai-cylindrical ridge. 

 The segments of the side lobes are each of them provided with a triangular 

 projection, with its point directed forward, as may be seen in the figure. 

 They are also abruptly bent down at half their length, and near their 

 extremities curve a little outwards. The central lobe of the pygidium or 

 tail, consists of seven segments, and the lateral lobes of four or five each ; 

 these latter are flattened and marked with a small groove along their 

 centres, so that each generally has the appearance of two. A small 

 portion at the extreme point of the tail is not grooved. At the base 

 of the head a strong furrow extends from one angle across to the 

 other, and causes an elevated border upon the posterior margin, which 

 might be readily mistaken for one of the segments of the body. The 

 glabella is much narrower at the front than at the base, and divided into 

 three lobes, on each side. The front lobes are, at least in some specimens, 

 obscurely divided each into two others. The fxont of the head is turned up 

 into a broad beak. The eyes are small and situated nearly opposite the 

 second lobe of the glabella, and the whole surface, in perfect specimens, is 

 rough, with small irregular granules. This species very much resembles 

 the celebrated Calymene Blumenbachii, figured in all elementary books, 

 upon the science of geology, and is, in fact, considered by some authors to 

 be the same. It does not, however, agree with the figures given in the 

 best European works, particularly in the structure of the front part of the 

 head. In the English fossil, the glabella extends quite to the margin, but 

 in ours there is a space of about one eighth of an inch in specimens of the 

 size of Fig. 10, between the elevated beak and the rounded front lobe of the 

 glabella. This character alone certainly appears sufficient to warrant a 

 separation of the species. The specimen above figured was found in the , 

 Trenton limestone, at the Chaudiere Falls, near the City of Ottawa. The 

 central lobe has been flattened by pressure, so that it appears wider than it 

 would be, had it been preserved in its natural shape. The sides are also a 

 little bent under the body. The specimens of this locality are, most of them, 

 of the above dimensions, although separated heads are occasionally found 

 much larger. 



Calymene, Greek, " concealed," senana, " ancient." 



