238 



lengthened into a genal spine, which, from the facial suture to the point, 

 is as long as the posterior extension of the suture behind the eyelobe. 



The movable cheek, under the eyelobe, carries a convex band of several 

 rows of minute ocular facets arranged diagonally ; those in front of the 

 middle of the band run diagonally upward and forward, those behind 

 the middle run diagonally upward and backward. 



The thorax of eight joints has long, narrow segments, terminating in 

 rounded points, strongly facetted ; the ring of the middle segment is 

 about as long as the pleurae ; the pleurae are bent (but scarcely geniculate) 

 at one-half of the length of the first segment ; they bear a quite shallow 

 furrow directed backward ; each ring of the thorax has a narrow articulat- 

 ing band. 



A thorax and pygidium of smaller size, supposed to belong to this 

 species, has the following characters ; The pygidium is broadly semi-cir- 

 cular and no axis is visible ; a slight protuberance one-third from the 

 posterior end indicates the termination of the rachis ; the sides lobes are 

 sloped down to a somewhat flattened margin. On each side lobe there 

 is a shallow groove near the front. 



The hypostome in this species is unknown, therefore the reference to 

 Asaphellus is provisional. 



Sculpture. The surface of the shell of this trilobite is smooth or 

 minutely punctate. The underside of the movable cheek has a rugulose 

 surface on the upper part, and a finely concentrically striated band on 

 the slope outside of this ; the flattened band is covered with widely spaced 

 anastomosing raised lines, parallel to the margin of the shield. 



Distinct from The composition of the test in this species is different from that of A. 

 Homfrayi, which has a shining and polished surface as preserved in the 

 shale ; this, on the contrary, had a dull surface, and appears to be more 

 calcareous, as there is little but a film of the shell substance left, where 

 the containing shale has been exposed to weathering. 



Size. Length, about 70 mm. ; width, about 55 mm. ; length of head 

 shield about 26 mm. ; of the thorax, 20 mm. ; of the pygidium, about 24 

 mm, The pleurae are about 45 mm, long, and the pygidium of about the 

 same width. Scarce. 



Horizon and locality. The gray shales of Assise C. 3 c. 2 at McLeod 

 brook, Boisdale N.S. 



A. ( 1 ) planus is distinguished from A. Homfrayi, var. by its broader 

 glabella, more prominent and more distant eyes, broader and less pointed 

 front to the middle piece of the headshield, more obscure neck furrow, 



