236 



Cheieurds pleueexanthemus, Green. 



Ceraur us pleurexanthemus, Gveen 1832. Mon. Trilob. N. Aimer., p. 83, cast 



33, pi. 3, ag. 10. 



Hall 1847. Pal. N. York, vol. I., p. 242, pi. 65, 



figs. 1, a-n, and pi. 06, figs. 1, a-h. 



Cheirurus pleureocanthemus, Billings 1863. GeolJ Canada, p. 188, fig. 188. 



Ceraurus pleurexanthc7/ius, 'Wsilcott. . . 1881. Bull. Mus. Comp. Zool. Harvard 



Coll., vol. VIII., p. 211, pi. 5, figs. 1-6. 

 Clarke 1894. Lower Silur. Trilob. Minn., p. 734. 



A few specimens which have since been identified with this well known 

 eastern species were collected at Lower Fort Garry (St. Andrews) by 

 Dr. Bell in 1880, and by T. C. Weston and A. McCharles in 1884 ; "also 

 at Ea^t Selkirk by Mr. McCharles in 1884. A badly preserved cast of a 

 glabella, which is also apparently referable to C pleurexanthemus, was 

 collected at Big Sturgeon Island, Lake Winnipeg, by D. B. Dowling and 

 L. M. Lambe in 1890. 



Staokocephalus. (Species undeterminable.) 



Two specimens of the spherical anterior termination of the glabella of 

 a species of Staurocephalus, each followed by a short and not very deep 

 transverse constriction, were collected by Mr. Weston in 1884, the larger 

 one at Lower Fort Garry and the smaller at East Selkirk. In the larger 

 one the spherical portion is five millimetres broad, and about a quarter 

 of a millimetre less in length. 



LiCHAS (Platymetopus) cucullus. 



Lichas cucullus. Meek and Worthen .1865. Proc. Ac. Nat. So. Philad., vol. XVII., 



p. 266. 

 1868. Geol. Surv. 111., vol. III., p. 299, pi. 



1, figs. 6, a-c. 

 Platymetopus cucullus, Clarke' 1894. Lower Silur. Trilob. Minn., p. 746, 



figs. 66 and 67. 



'^=Lichas TreiUoncnsis, Conrad. 



dr. Asaphus? Trentonensis, GouTaA 1842. Journ. Ac. Nat. Sc. Philad., "ol. 



VIII., pt. 2, p. 277, pi. 16, fig. 16 ; and 



Platynotus Trentoncnsis, Hall 1847. Pal. N. York, vol. I., p. 235, pi. 64, 



figs. 1, a-e. 



East Selkirk, A. McCharles, 1884 : three heads, which are now in the 

 Museum of the Survey. These agree very well with the descriptions and 

 figures of Lichas or Platymetopus cucullus, but, on the other hand, they 

 can scarcely be distinguished from heads from the Trenton limestone at 

 Hull, Que., which are believed to be referable to Lichas Trentonensis. 

 "The slight concavity of the median lobe of the glabella" of L. cucullus 

 "on its posterior slope, which gives it a peculiar subconical protuberance,'' 



