ANTICOSTI ISLAND FAUNAS. 
35 
Horizon and Locality. Ordovician ; Charleton (3), Charleton 
point. 
The holotype and only known specimen is in Peabody 
Museum. 
Phylum, Arthropoda. 
Class, Crustacea. 
Subclass, Trilobita Walch. 
Order, Opisthoparia Beecher. 
Family, Olenidae Burmeister. 
Genus, Triarthurs Green. 
Triarthrus becki var. macastyensis new variety. 
1910. Triarthus spinosus Schuchert and Twenhofel, Bull. Geol. Soc. Am., 
vol. 21, p. 694. 
This new form is like T. becki except in one respect. The 
facial sutures are slightly more sinuous and in front they diverge 
from the axis instead of converging as in T. becki. The glabella 
of the most perfect specimen is 3.5 mm. wide; 4.5 mm. long; the 
entire cephalon 5 mm. long. That it grew to a larger size is 
proven by a specimen which has the cephalon at least 8 mm. long. 
The same type of facial suture i» seen in the T. becki from the 
Collingwood black shale of Ottawa, Canada, and Doctor Ruede- 
man has called the writer’s attention to the fact that T.jemtlandi- 
cus Lindstrom has a similar facial suture, though otherwise 
different. 
Horizon and Locality. Ordovician; evidently present in 
considerable abundance in the Macasty black shales. 
The holotype and a single paratype are in Peabody Museum. 
