[MATTHEW ] CAMBRIAN FAUNAS 109 
There is no example of this form in the Walker or Canad. Surv. 
Collections. 
“ACROTRETA GEMMA, Var. DEPRESSA, 1. var.” 
“The specimens from Mt. Stephen are relatively much lower and 
broader in proportion to the height than the typical forms of A. gemma. 
On this account they are considered as a variety.” 
Mr. Walcott writes to me to say that the dorsal which he referred 
to Linnarssonia sagittalis Salt, he now thinks to be the dorsal valve of 
of the above species. 
In the Walker collection is a dorsal valve which, by its sharp 
median septum and other features, appears to be the dorsal valve of 
this Acrotreta; the species appears to be sufficiently distinct from 
A. gemma and may be called A. depressa, Walcott. 
“ ORTHISINA ALBERTA, 0. sp.” 
“ Shell transversely suboval, front broadly rounded; the straight 
hinge-line is shorter than the full breadth of the valve; the area of 
the ventral valve high, bent backward from the hinge-line, divided 
by a large foramen that is covered by a convex deltidium. The area 
of the dorsal valve slopes back at about a right angle to the valve. 
The broad short foramen appears to have been covered by a low 
deltidium. 
Surface marked by radiating coste five in the distance of 3 mm. 
on the frontal margin. 
This species recalls Orthis Lindstrom, Linrs. from the Paradox- 
ides zone of Sweden.” 
Examples from the Walker collection are not well preserved and 
show no further characters. 
There is another Orthid in the Walker collection, with ribs much 
wider apart, but not in good preservation. 
“ KUTORGINA PROSPECTENSIS, Walc.,?” + 
“A fragment of a species of Kutorgina, closely related to 
K. prospectensis, occurs on slate in association with Ptychoparia 
Cordillere. 1t not improbably represents a new species.” 
No example of this was found in the collections that passed under 

? Am. Jour. Sci.. Vol. XXXVI., Sept., 1888, p. 166. 
