New Genera and Species of Brachiopoda. 1$1 



ARTICLE IX. — On some new Genera and Species of Brachi- 

 opoda, from the Silurian and Devonian Rocks of Canada. 

 By E. Billings, F.G.S. Read before the Natural History 

 Society of Montreal, 28th March, 1859. 



{From the Report of the Geological Survey for 1858.) 

 Genus Centronella, Billings. 

 Generic Characters. — Shells, having the general form of Tere- 

 hratula. Dorsal valve, with a loop consisting of two delicate 

 riband-like lamellae, which extend about one-half the leno-th. 

 These lamellae at first curve gently outwards, and then approach 

 each other gradually, until at their lower extremities they meet 

 at an acute angle ; then becoming united they are reflected back- 

 wards towards the beak in what appears to be a thin flat vertical 

 plate. Near their origin each bears upon the ventral side a single 

 triangular crural process. Name from the , Greek, Kentron, a 

 spur. This genus is intermediate between Terebratula «#nd 

 Waldheimia. In the former the loop is short, not exceeding 

 greatly one-third the length of the shell and not reflected. In the 

 latter it extends nearly to the front and is reflected but the 

 laminae are not united until after they are folded back. 



The following figures will explain the difference more clearly : 



I 



6 7 



Ventral, side, and dorsal views of Centronella glans- 



fagea. 

 Interior of dorsal valve, shewing the loop. 

 Longitudinal section, shewing the position of the loop 



in the interior. 

 Interior of dorsal valve of Terebratula. I, the loop. 

 Interior of Waldheimia. Z, the loop. 



