112 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



specimens examined, and in figure b, a longitudinal section of the type 

 specimen, continuous tabulae are represented as stretching across the 

 visceral chamber with no indications of septa ; the specimen itself shows 

 dissepiments that arch upward and inward on either side, but that are 

 unusually flat at the centre, and primary septa that cut into the 

 dissepiments and disturb their regularity at the centre. 



Streptelasma angulatum, Billings. (Sp.) 



Petraia angulata, Billings. 1862. Palseoz. Foss., vol. I., p. 103, figs. 90 a and b. 

 ii Billings. 1866. Cat. Sil. Foss. of Anticosti, p. 7. 



Original description. — " Of this species we have only three small speci- 

 mens. They are irregularly conical, moderately curved, expanding from 

 an acute point to a width of seven lines at a height of about eight lines, 

 acutely angulated on the side opposite the concave curve. Surface with 

 a few obscure annulations of growth, and besides engirdled with numer- 

 ous smaller obscure lines, from four to six in one line. The cup appears 

 to be about four lines deep in a specimen eight lines in length. There 

 appear to be three or four septal striae on the outside in the width of one 

 line. The specimens being imbedded in stone, the number of the septa 

 cannot be ascertained. 



"The distinctive character of this species consists in its acutely angular 

 shape." 



Localities. — Island of Anticosti, Que. at Charleton Point and at the 

 west end of the island, collected by J. Richardson, 1856 ; Hudson River 

 formation. 



Transverse and longitudinal sections of the type specimens of S. 

 angulatum show that the cup is equal in depth to one-half the height of 

 the corallum, the septa number about seventy-five and are alternately 

 long and short, the former reach the entire whilst the latter are quite 

 diminutive. Further details of structure are not clearly shown; the 

 specimens are small and probably immature. 



The angularity of the convex curve of the corallum is a noticeable 

 feature of some of the specimens of S. robustum, Whiteaves, from the 

 Galena-Trenton formation of the Red River valley, Manitoba, and 

 it is not in the western species considered to be a character sufficiently 

 reliable for specific differentiation. 



Possibly the species S. angulatum is founded on young, angulated 

 specimens of S. selectum, Billings. 



