OEGANISMS IN ACADIA. 151 



Size.— The longest example preserved was 12 mm. loug. Width, 2 ram. Lougth of 

 joints, J mm. Diameter ol' the canal, about li- mm. 



Horizon and Locality.— In grey layers of the red sandy shales of Div. 2 of the Basal 

 series at Caton's Island, Grreenwich. N.B. 



Dr. Schmidt thinks these fossils may be compared to the long arms of the American 

 species, Eocysliles longidadylus, Walcott, of the Middle Cambrian of Nevada, D. S., but I 

 have found no body plates of cystids with the Canadian Platysolenites. 



v.— BRAC!HI0P01>A. 



OBOLUS, Eiihwald, 1829. 



Obolus pulcheb. Mall. (PI. VIII, figs, la-m and 2a-c.) 



Can. Record of Sci., Jan., 1889, p. 303. 



The original description of this species was as follows : — 



General outline nearly orbicular ; the valves gently, but rather flatly and evenly 

 arched downward from the centre all around, except that the dorsal is flatter at the back 

 than elsewhere, and the ventral valve runs out into a short, acuminate umbo. 



Dorsal valve somewhat wider than long ; more strongly arched toward the front than 

 elsewhere ; somewhat elevated at each end of the hinge line. 



Ventral valve about as wide as long ; the front evenly rounded ; back produced into a 

 short pointed beak, angle of incidence of the two sides 110° to 120°. 



Sculpture of the posterior half of the valves, consisting of miniite tubercles, sloping 

 forward and arranged in rows, which arch forward across the mesiau line from each 

 lateral margin, giving the surface a cancellated appearance, like ÛiaX oi Ling iila {?) favosa 

 and Kutorgina pannula. Sculpture of the anterior part on the front and sides in the adult 

 shell consisting of concentric lines of growth, with faint, interrupted, radiating striie. 



One of the most interesting species among the early brachiopods of the St. John group 

 is the one named above On account of its antiquity and because of its peculiar form in 

 the embryonic stages, the writer now gives considerable space to the description of its 

 characters. It is the oldest species of brachiopod belonging to the St. John group, of 

 which good material has been obtained, and the following extended account is based on 

 this material. 



The ventral valve is evenly and moderately arched, except that the sides are depressed 

 toward the beak ; the beak itself is prominent only toward the tip, and runs out hori- 

 zontally from the middle of the valve. 



Interior of the Dorsal Valve (Figs. 1 z to m). — The most noticeable feature of the interior 

 of this valve is the three ridges which radiate from the hinge line toward the anterior end 

 of the valve. The mesian ridge begins with a small tubercle near the umbo, is longer than 

 the two lateral ridges, and divides into two outward arching forks; including these, it 

 extends about two-flfths of the length of the yalve from the hinge line ; its posterior part 

 divides the pits of the hinge line where the posterior adductor muscles were attached. 

 The two lateral ridges extend forward from the two ends of the hinge line ; and at the end 

 of each, where it joins the hinge line, are situated the pits due to the attachment of the two 



