378 



New Species of Trilobites. 



Locality and formation. — Is 1 and of St. Joseph, and on the 

 island west of Grant's Islands, Lake Huron ; also at the Falls of 

 La Petite Chaudiere, township of HuU. Black River limestone 

 or base of the Trenton. 



Collectors. — A. Murray. E. Billings. 



Ill^enus conifrons. (n.s.) 



Fig 11. 



a Upper surface of head. The dorsal furrows are straight instead 



of curved, as they are in this figure. 

 b Side view. 



Description. — This species is closely allied to I. angusticollis, 

 but differs therefrom by having the glabella or central lobe ex- 

 panded and elevated so as to form a large conical protuberance 

 on the front half of the head. In the best preserved specimen 

 the head is strongly trilobed behind by the deep dorsal furrows 

 which are parallel and distant four and a half lines from each 

 other for four lines forward, when they curve outward to the 

 width of seven lines, then curving inward they unite in front ; 

 the furrow in front of the glabella runs along for five lines at a 

 distance of one line from the margin and parallel with it. This 

 is the appearance of the furrow on the cast of the interior of the 

 head, but it is most probable that when the crust is preserved, 

 it is only obscurely indicated in the front half of the head. 

 The central lobe is very convex, and has the elevation and form 

 of one-third of a cylinder so far forward as the dorsal furrows 

 are parallel; it then expands to nearly twice its width and is con- 

 ically inflated so as to project forward, and overhang the front 

 margin. On a side view the dorsal ouiline of the head is nearly 

 straight, or gently convex for the length of seven lines, but in the 

 next three lines it makes a short rounded curve which changes 

 the direction about 100° downwards on which course it continues 

 in nearly a straight line to the front margin. (See Fig. 11.) The 

 height of the most elevated point of the head above the front 

 margin is six lines. 



