102 



addition to the principal groove exhibits two or three other obscure farrows 

 on each side. This may constitute a distinct species. 



This curious fossil is evidently generically identical with that figured by 

 Prof. Hall in the 2nd vol. Pal. N. Y., PI. 9, under the name of Rusophy- 

 cus bilobatus, but differs therefrom specifically in being proportionally 

 shorter, while the furrow does not run the whole length, as it does in the 

 Clinton species. 



Locality and Formation. — Head of the Grenville Canal ; in the Chazy 

 sandstone. 



Collector. — Sir W. E. Logan. 



ZOOPHYTA. 



Petkaia aperta. (N. sp.) 



Fig. 89. Fig. 90. 



Fig. 89. — Petraia aperta. — a, Side view ; 6, interior of cup. 



90. — P angulata. — a and b, Two views of this species. 



Description. — Corallum simple, turbinate, short, widely expanding; cup 

 deep, broadly concave in the bottom, with a distinct septal fossette on one 

 side. Radiating septa from 100 to 150. Surface with a few annulations 

 of growth, and finely marked with the longitudinal septal striae, of which 

 there are from 5 to 7 in the width of one line. The specimens are from 

 4 to 6 lines in height, and from 8 to 12 Imes in width at the margin. 

 Depth of the cup about half the height. The pomt of attachment is very 

 nearly central. 



In the 1st vol. of the Paleontology of New York, PI. 12, Prof. Hall 

 has figured two species mider the name of Streptelasma profunda. It is 

 possible that the specimen represented by his fig. 4, on the plate quoted, 

 may be an individual of this species, but the figure does not exliibit any 

 indications of a cup, or any external characters to prove that it belongs to 

 this genus, or indeed that it is a coral at all. The other five figures are 

 sections of a species of Petraia. He describes P. p>roftmda as having 

 the cup extending nearly to the base of the coral, and having from 36 to 

 60 radiating septa. In the Black River limestone in Canada, there is a 



