EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 39 



the interior the ventral valve shows a deep muscle scar and strong dental 

 plates, the former not being striated by the plications of the shell. On the 

 dorsal valve is a defined cardinal area, perforated hinge plate and narrow 

 elongate muscle area divided by a faint median septum. 



We have spoken elsewhere of the relations of this and similar shells to 

 Trigeria and of the presence of such forms both in the Oriskany and Hel- 

 derberg faunas. We have identified in the Cumberland Oriskany, Tri- 

 geria gaudryi OEhlert [see Palaeontology of New York, v. 8, pt 2, pi. 

 76, fig. 6, 7] and T. portlandica Billings from Square Lake, Me. is a 

 somewhat similar shell. Both however lack the specific characters of the 

 shell before us. 



Horizon. Very abundant in nos. 11, 13. 



Sieberella pseudogaleata Hall 



Plate 7, figures 24-26 



Pent a m ems pseudogaleatus Hall. Palaeontology of New York. 1S59. 3:259, 



pi. 48, fig. 2 a-i 

 Sieberella pseudogaleata Hall & Clarke, op. cit. v. 8, pt 2, pi. 72, fig. 14 



Specimens of this Helderbergian species abound in the lowest beds of 

 the series though very seldom well preserved. 

 Horizon. No. 1. 



Camarotoechia 



The species present at Dalhousie are poorly preserved, being badly 

 crushed and it is not easy to arrive at a satisfactory conclusion as to their 

 affinities. Two at least are present, one a coarsely plicated shell with a few 

 ribs, three in the sinus, all bearing very strong imbricating, concentric 

 growth lines and presenting an unfamiliar aspect. Another suggests C. 

 formosa Hall — a Helderberg species. 



Spirifer concinnus Hall 



Plate 8, figures 1-16 



Spirifer concinnus was described and fully illustrated by Hall 

 in the Palaeontology of New York | 1859. 3 : 2 °°> P^ 2 5> fig- 2 a "i '< pi- 

 28, fig. 7] and is one of the common species of the Helderberg (New Scot- 

 land) fauna. It has certain well defined differentials: a low broad median 

 sinus and prominent fold, prominent ventral beak and area, linguate anterior 

 extension of the sinus, full umbones in both valves, a rather elongate out- 

 line fore and aft, 6 to 7 rounded ribs on each lateral slope and the surface 

 covered with fine, sharp, crowded and elevated concentric striae which have 

 been described as granulose on the edges but which are really fimbriate with 

 a single row of minute spinules. 



The most abundant spirifer at Dalhousie is of this type and is doubt- 



