350 AxxAi.s OK JHE Carnegie Museum. 



" Anterior edge of the pygidium convex at the axial lobe, obliquely 

 truncated from the fulcrum, the axis either not at all or very obscurely 

 defined. 



" Surface smooth, with the exception of the front of the head, where 

 there are, at the margin, the usual transverse fissures. 



" This species was discovered by Admiral Bayfield, R. N., during his 

 survey of the Gulf of St. Lawrence. A well preserved specimen is in 

 the Cabinet of the (geological Society of London among the fossils 

 presented by Admiral Bayfield. During the present year, 1859, Sir 

 W. E. Logan visited the Mingan Islands and i)rocured numerous 

 specimens at Trilobite Bay, the original locality. 



" Dedicated to the discoverer, Admiral Bayfield. 



'■'■ Locality and FovDiation. — Trilobite ]>ay, Mingan Islands, 

 Chazy." Type in Ottawa Museum. 



Illaenus globosus Billings. (Plate 13, figures 6, 7.) 



Jlhenus glolwsus liillings, 1S59, Canadian Naturalist and Geologist, volume I\', page 

 367, figures 1-3. 



This little species is very common in the Chazy of the northern. part 

 of the Champlain Valley, especially in the reef material where there 

 are pockets which consist almost entirely of the separated head and 

 abdomen shields of this one trilobite. The axis of the thorax is very 

 wide and the pygidium smooth and undifferentiated like Biiinastus. 

 The head, however, shows fairly strong, though short dorsal furrows, 

 and the furrows on the thorax, while very far apart, are deeply 

 impressed. 



Description. 



Cephalon short, broadly rounded, and steeply convex toward the 

 front and at the sides. Frontal margins striate and incurved. Dorsal 

 furrows short, directed obliquely inward, with a slight outward curve 

 at the anterior end. Eyes small, far back, and very far apart. Free 

 cheeks also small, steeply sloping. Genal angles rounded, extending 

 a little back of the posterior margin of the cranidium. Shell smooth, 

 not punctate. Thorax of ten segments. Axis very wide, dorsal fur- 

 rows deep, and paralleled by ridges, in passing over which the seg- 

 ments turn forward and then backward. 



Sides steep and the ends of the segments directed backward. Py- 

 gidium regularly rounded, very convex, without any trace of the axis 

 except at the anterior margin. The whole trilobite is oblong, taper- 

 ing only a little. 



