New Species of Trilobites. 



367 



LEPERDITIA ANNA, (Jones). 



L. anna, (Jones) Annals of Natural History, 3rd series, vol. 1, 



p. 247, plate ix., fig. 18. 

 Canadian Fossils, Decade 3, p. 96, plate xi., fig. 13. 



This species has been found only at the original locality in a 

 quarry near the Station House of the Grand Trunk Railway, St. 

 Anns. 



ARTICLE XXVIII. — Descrijytions of some new species of Trilo- 

 bites from the Lower and Middle Silurian rocks of Canada. 

 By E. Billings. 



(Extracted from the Report of the Geological Survey of Canada for 1858- 



1859.) 



Illaenus globosus. (N. s.) 



Fig. 1. 



Fig. 2. 



Fig. 3. 



Fig. 1. — Illcenus globosus. View of the thorax of a specimen rolled up. 

 2. — Side view of same specimen. 

 3. — View of pygidium of the same. 



Description. Oblong, oval, distinctly trilobed, the central lobe 

 very broad, full half the whole width. Length two to three inches, 

 width half the length. Head rather more than one third, the 

 thorax about one third and the pygidium rather less than one 

 third the whole length.* 



The head is large, very convex, most prominent in the centre 

 and in form about one fifth more than the quarter of a sphere ; 

 the dorsal furrows continued on it about one third the length, sub- 

 parallel, a little curved outwards at their anterior extremities 

 distant from each other half the width of the whole head ; cheek 



* All the measurements of the head and pygidium given in this article 

 (unless otherwise stated) were made by placing one point of the divi- 

 ders at the centre of the anterior, and the other at the centre of the pos- 

 terior margins. The figures would be different if the length were in all 

 cases taken from the most forward projecting point, and this would be 

 the proper mode, provided we knew how the animel carried its head. 



