233 



Most of the trilobites from the Winnipeg and Red River limestones 

 have scarcely any portion of the crust preserved, and the specimens 

 referable to Asaphus or liotelus in particular are often so imperfect that 

 it is scarcely possible to ascertain whether they had genal spines or not. 

 In addition to the four specimens here identified with Asaphus (Isotelus) 

 Susce, which are probably not sufficiently distinct from /. gigas, an 

 imperfect left free cheek of a large Isotelus, with the genal angles dis- 

 tinctly rounded, which appears to be referable to /. gigas, was collected 

 at Cat Head by D. B. Dowling and L. M. Lambe in 1890. This speci- 

 men must have been about twenty inches in length when entire. The 

 maximum diameter of the eye is twenty millimetres, and the breadth of 

 the cheek, immediately below the eye, is four inches and a half. 



Several small specimens of an Isotelus, which do not show the charac- 

 ters of the genal angles at all clearly, but which are also probably referable 

 to I. gigas, were collected at Cat Head by Mr. Weston in 1884, and by 

 Messrs. Dowlins; and Lambe in 1890; at Kinwow Bay by Mr. Weston 

 in 1884; and at Inmost or Birch Island by Mr. Weston in 1884 and by 

 Me.ssrs. Dowling and Lambe in 1890. The largest of these specimens 

 are from three and a half to fuur inches in length. One of the specimens 

 from Inmost Island is nearly entire, though most of the test is exfoliated, 

 and one from Cat Head is a natural mould of the exterior of the dorsal 

 surface of an entire specimen. In each of these, the cranial shield and 

 pygidium are narrowly rounded or somewhat pointed in the middle. Two 

 of the specimens from Inmost Island are separate glabellse ; two, cephalic 

 shields with the lower surface exposed and showing the doublure, one 

 with the hypostoma in place ; and one is a small separate hypostoma. 



Asaphus (Isotelus) maximus, Locke. 



Isotelus niarciriius, Locke 1838. Second Ann. Rep. Geo]. Surv. Ohio, 



p. 246, fig. 8 and 9. 

 Isotelus mcgistos, Locke 1841*. Trans. Amer. Assoc. Geol. and Nat., 



p. 221, pi. 6. 

 Asaphus mc'jistos, Billings 1863. Geol. Canada, p. 184, fig. 182, and p. 



951. 

 II II II 186G. Geol. Surv. Canada, Cat. Silur. Foss. 



Isl. Anticosti, p. 26. ^ 



Isotelus maximus, Clarke 1894. Lower Silur. Trilob. Minn., p. 701, 



and fig. 5 on p. 703. 



An imperfect free cheek of a huge trilobite which may be referable to 

 this species, with a well developed spine at the genal angle, was collected 

 at Cat Head by D. B. Dowling and L. M. Lambe in 1890. Although 

 imperfect at both ends the actual length of this free cheek is upward of 

 seven inches. 



* But, in the "Report of the Geology of Ohio," vol. I. (1873) p. 159, Meek gives 1842 

 and 1843 as the dates on which the species was described under this name. 



