100 



Variety 

 puteis. 



Acrothele 

 abavia. 



A. AVIA-PUTEIS. PI. IV, figs 5 a and b. 



Bull. Nat. Hist. Soc. of N. Brunswick, Vol. IV, p. 398, pi. XVI, figs. 

 5, a b. 



This seems to be a variety of A. avia. It differs in the possession of a 

 pair of pits, one of which lies on each side of the space between the fora- 

 men and the visceral callus, partly overlapping each. The visceral callus 

 is quite short in this form and has but little prominence. The ridges on 

 the surface of the valve are more regularly concentric than in the type, 

 and more sharply cut ; about ten are found in the space of one millimetre. 

 The cardinal area is curved forward towards the top, and finely striated. 

 The foramen is about a fifth of the length of the valve from the cardinal 

 line, and the front of the callus about a third. Vascular trunks and 

 branches are visible on the surface of the ventral valve as in the type. 

 The dorsal valve does not sensibly differ from that of A. avia. 



Size. The largest valve seen was 8 mm. long, and about the same 

 width. 



Horizon and locality. Found in the Bretonensis shale (E. 3d.) at 

 Gregwa brook, Escasonie, Cape Breton. Frequent. 



ACROTHELE ABAVIA. PI. IV, figs. 3a to d, and 4a and 6. 



Bull. Nat. Hist. Soc. of N. Brunswick, Vol. IV, p. 398, pi. XVI, figs. 

 3 a-c?, and 4 a and b. 



Outlines of the valve nearly circular. Length of the hinge line less 

 than a third of the diameter of the valve. 



Ventral valve rather flat, with the umbo slightly raised. The umbo is 

 about one-quarter of the length of the valve from the cardinal line. In- 

 terior. In the examples known from the horizon E 3a., the interior is 

 smoothly moulded, except along the front slope, where faint vascular 

 grooves may be detected, but in those from E. 36., a visceral callus is 

 faintly outlined, with a swelling on the middle ; some valves here have faint 

 impressions of vascular trunks on each side of the callus, running forward. 



The dorsal valve has its greatest height near the middle, and has an 

 appressed umbo, close to the hinge line ; the lateral margins, in the pos- 

 terior half, are revolute. Interior. A median septum starting near the 

 hinge line, extends across the middle of the valve to nearly one-third 

 from its front ; it is widest in the middle and fades away to a point in 

 front. On each side of it is a vascular grove, the pair radiating from 

 near the umbo and extending nearly to the front margin ; they are nearly 



