Raymond & Narraway : Notes on Ordovician Trilobites 249 



Chazy form are much smaller than those of the Trenton specimens, 

 and nearly circular, instead of triangular, in cross section. 



Judging from Clarke's figures of Thaleops ovata (Paleontology of 

 Minnesota, Vol. Ill, pt. 2, p. 718, fig. 28) it is possible that Thaleops 

 arctura occurs in the Trenton. The genal spines of the specimen 

 there delineated approach much more closely to the form observed 

 on our specimens from the Chazy at Crown Point and elsewhere than 

 they do the spines on the specimens collected by Mr. Narraway in the 

 Black River near Ottawa. 



We have not yet been able to seize upon characters which will 

 serve to distinguish the specimens usually found, namely, the detached 

 cranidia and pygidia. 



Subgenus Bumastus Murchison. 



Bumastus milleri (Billings). 



(Plate LXI, figures 9, 10; Plate LXI, figures 3-5.) 



Cf. Illcenus trentonensis Emmons, 1842, Geology New York, Report 



of Second District, p. 390, fig. 3. 

 Illcenus milleri Billings, 1859, Canadian Naturalist and Geologist, 



Vol. IV, p. 375, fig. 10. 

 Illcenus milleri Walcott, 1877, Advance Sheets, Thirty-first Annual 



Report, New York State Museum Natural History, p. 20. 

 Illcenus milleri Walcott, 1879, Thirty-first Annual Report New York 



State Museum Natural History, p. 71. 

 Cf. Bumastus trentonensis Clarke, 1897, Paleontology of Minnesota, 



Vol. Ill, pt. 2, p. 718, figs. 30-35. 

 Cf. Bumastus trentonensis Weller, 1902, Paleontology New Jersey, 



Vol. Ill, p. 194, PL 14, figs. 8-13. 



In the " Paleontology of Minnesota," Dr. Clarke referred to Illcenus 

 milleri as a synonym of Bumastus trentonensis (Emmons), reviving the 

 latter name for the smaller of the Illceni described by Emmons. 

 (See the description of the following species for a fuller account of 

 these names.) Emmon's name Illcenus trentonensis was applied to a 

 specimen found in the Black River or Trenton Limestone at Water- 

 town, New York, and though figured, this specimen was not described. 

 The present location of this specimen does not appear to be known, 

 so only the figure is left to define the species. Under these circum- 

 stances we cannot agree with Dr. Clarke in superseding Billings' 



