ANTICOSTI ISLAND FAUNAS. 
25 
Foramen narrow, about 0.25 mm. wide, sides almost parallel, 
extends to the beak and finds its other continuation in the 
dorsal valve. Wetting of the ventral area shows that narrow 
side plates are annexed to the sides of the foramen; these are 
supposed to be continuous with the teeth, as in 0. bouchardi, 
the nearest related species. These plates simulate deltidial 
plates with which, however, they are probably in no way homol- 
ogous. 
This species finds its nearest relative in 0. bouchardi David- 
son, from the Wenlock of England and Scotland, from which it 
differs in having no ventral sinus, the sides of the foramen 
parallel instead of converging to the beak, the ventral area 
making a right instead of an acute angle with the plane of the 
lateral margins, no longitudinal striations on the area such as 
exist in that species, and in being more finely plicate with all 
the plications reaching the beak. That species also has the 
ventral area curved and the beak incurved. 
Horizon and Locality. Ordovician; Ellis bay in zone 5 of 
the Ellis Bay formation. 
The holotype is in Peabody Museum, Yale University. 
Only a single specimen has been collected. 
Superfamily, Strgphomenacea Schuchert. 
Strgphofrian new subgenus. 
The above subgeneric term is proposed for those resupinate 
forms of the Strophomenidae which are like Strophonella except 
that they have some ten or a dozen denticulations along the 
hinge line instead of a completely denticulated hinge margin. 
That is, these forms mark the inception of the Strophonella 
stock, Strophoprion holding the same relation to Strophonella 
that Brachyprion does to Stropheodonta . In one line of devel- 
opment there are Sirophomena — -Strophoprion — Strophonella ; 
in the other Rafinesquina — Leptaena? {ceres — nitens stock, not 
rhomboidalis ) — Brachyprion — Stropheodonta. The type of Stro- 
phoprion is Strophoprion geniculatum (Shaler) ( Brachyprion 
geniculatum Shaler, Bull. Mus. Comp. Zool., vol. 1, No. 4, p. 63, 
1865). 
