300 Canadian Record of Science. 



Trilobita. 

 Acidaspis perarmata. (Sp. nov.) 

 Plate iii, fig. 6. 



Body depressed, very slightly convex, its general outline, 

 apart from the marginal spines, longitudinally subelliptical 

 and a little longer than broad. 



Head about twice as broad as long, occupying one third 

 of the total length, exclusive of the spines on the pygidium : 

 its front margin broadly subtruncate, nearly straight but 

 faintly sinuous and very obscurely three lobed, with a slight 

 indentation on each side of the glabella immediately in front 

 of the anterior termination of each of the ocular ridges : its 

 posterior margin much more distinctly flexuous and curved 

 backward in the centre with a moderately convex curve, 

 and forward with a shallowly concave curve, on each side. 

 Eyes small, placed very near the posterior margin of the 

 head and opposite the most contracted portion of each of 

 the free cheeks: ocular ridges moderately prominent, 

 slightly curved and converging obliquely forward from the 

 eyes to their terminations near the frontal margin, where 

 they are about twice as close together as at their commence- 

 ment anteriorly. Characters of the glabella unknown. 

 Outer margin of each of the free cheeks somewhat ex- 

 panded anteriorly and forming a not very prominent 

 rounded lobe, which is armed with eight very short pointed 

 spines — slightly contracted behind the midlength and ter- 

 minating posteriorly in a straight and pointed genal spine, 

 which is a little shorter than that of the pleura of the first 

 abdominal segment, and diverges outward and backward at 

 an angle of 40° to a line drawn at a right angle to the 

 longitudinal axis. 



Thorax arched upon the axis, depressed and flattened on 

 the pleura? : composed of nine segments : axis occupying 

 more than one third of the entire breadth without the 

 spines, and narrowing very gradually to the posterior end : 



