Aurora Borealis, 383 



the body and pygidium there are altogether nineteen segments, of 

 which it is probable fourteen or fifteen belong to the tail, the precise 

 number not determined. The front margin of the head is very 

 obtuse, being in some specimens straight for more than half the 

 widih and in others even a little emarginate in the middle. The 

 tail is either broadly rounded, or slightly emarginate at the ex- 

 tremity. I think that when perfect and not at all flattened by 

 pressure, this species must be rather convex and its width a good 

 deal less than half the length . From the size of several of the 

 fragments, large individuals are probably three inches long, but 

 the more common length is from one to two inches. 



Locality and formation. — Lake St. Johns, Utica Slate. 



Collector. — T. Richardson. 



The three species of Iriarthrus known in Canada may be thus 

 distinguished : — 



1. Triarthrtjs Beckii. (Green.) 



A row of short spines along the middle of the axis of the 

 thorax. 



2. Triarthrus spixosus. (Billings.) 



A long slender spine from the middle of the neck segment of 

 the glabella, a similar spine from the eighth segment of the axis of 

 the thorax, and two others from the posterior angles of the head 7 

 one on each side probably attached to the cheek pieces. 



3. Triarthrus glaber. (Billings.) 

 With no spines either on the thorax or the head. 



ART. XXIX. — On the Aurora Borealis of the 28th of August 

 1859, By Charles Smallwood, M.D., LL.D., Professor 

 of Meteorology in the University of McGill College, Montreal, 



It is not the intention of the present short notice to endeavour, 

 however faintly, to record the splendid display of the Aurora 

 Borealis of the night of the 28th of August 1859,— to describe 

 its more than earthly grandeur, would far surpass all human efforts; 

 even to pencil its varied beauties, its gorgeous and ever chan- 

 ging tints, its crimson curtains of unusual splendour, suspended 

 as it were from the vast celestial vault, would far excel the powers 

 of human art : our object is to place on record some of the 

 Physical signs by which it was accompanied. 



