Raymond: Notes on Ordovician Trii.orites. 71 



The name Vofidcsia is given in acknowledgnienl of the debt which 

 students of the trilobites owe to Brie;- Tren. A. \V. N'^ogdes for his work 

 on the bibliography of the subject. 



Family ILL.>EN1D/E. 



Genus iLLiENUS Dalman. 



Subgenus Tiialeops Conrad. 



Thaleops arctura (Hall). 



Illcenus arciurus Hall, Paleontology of New York, I, 1847, 23, pi. 4bis, fig. 12. — 

 Emmons, American Geology, I, ii, 1855, 235, pi. 3, fig. 12. — Billings, Cana- 

 dian Naturalist and Geologist. IV, 1859, 379. 



Illantis ovalus Raymond, Bulletin American Paleontology, III, 1902, pi. 18, fig. 9, 



Thaleops ovata Raymond, Annals Carnegie Museum, III, 1905, 352, pi. 13, fig. 5. 



Thaleops arctura R.\ymond and Narraway, Annals Carnegie Museum, IV, 1908. 

 248, pi. 6r, fig. 8. 



Thaleops arctura and T. ovata were united as one species in my paper 

 of 1905, but later it was found by Mr. Narraway and myself that T. 

 arctura had longer and more angular genal spines and more elevated eye- 

 stalks than T. ovata. 



Subgenus Bumastus Murchison. 

 Bximastus globosus (Billings). 

 Plate XIX, figure 9. 

 On account of its broad axial lobe this common species is referred to 



Bumastus. 



Bumastus erastusi Raymond. 



Illanus erastusi Raymond, Annals Carnegie Museum, III, 1905, 351, pi. 13, figs. 



8.9- 



This species, which is quite common in the reefs at Valcour Island, was 



found by Professor Perkins to be extremely abundant at the same horizon 



on Isle La Motte. 



Bumastus limbatus sp. nov. 



Illcenus indeterminatus Raymond, (wow W.a.lcott), Annals Carnegie Museum, III, 



1905. 347. pl- 13. figs. I. 2. 



This species was first described as Illcenis indeterminatus, a species 

 which had never been adequately figured, but when Mr. Narraway sent 

 specimens of the real Bumastus indeterminatus from the Black River, it 

 was at once seen that there were important differences between the two 

 species. The dorsal furrows of B. limbo.tus are much less arcuate than 



