94 



valve are more conspicuous than the others, forming a more or less defined mesial fold ; upon 

 the dorsal valve there is a corresponding depression. The space between the valves leaves 

 little room for the spires, and these appendages appear to be somewhat loosely arranged, with 

 their apices approaching each other. These shells are apparently* fibrous in texture, and on 

 this account, and from the position of the spires, they approach more nearly to Atrypa than 

 to Trematospira, to the latter of which they are more nearly allied in external form " (Hall, 

 Pal. N. Y., Vol. IV., p. 328). 



Only one species of this genus, viz., C. concava (Hall), has as yet been recognized as 

 occurring in the Devonian rocks of Western Canada. 



114. CCELOSPIRA CONCAVA (Hall). 



Leptoccelia concava (Hall), Pal. N. Y., Vol. Ill, p. 245, PL XXXVIII., Figs. 1-7. 



Leptoccelia concava (Billings), Canadian Journal, New Series, Vol. VI., p. 352, Fig. 127. 



Coelospira concava (Hall), Sixteenth Report on the State Cabinet, p. 60. 



Ccelospira concava (Hall), Pal N. Y., Vol. IV., PI. LIIL, Figs. 13-19. 



Shell small, ovate, or sulj-orbicular, the width being equal to or a little less than the 

 length. Ventral valve convex, elevated along the middle, the beak small and incurved. 

 Dorsal valve flattened laterally ( and depressed in the centre, forming a shallow and obscure 

 mesial series. Surface with from ten to fourteen or more rounded radiating ribs, which occa- 

 sionally bifurcate. 



According to Hall, the dorsal valve has a small false area, and a triangular foramen 

 which is sometimes closed below by a deltidium. 



Average individuals of this species have a length of about three lines, and a width of 

 the same or a little less. Detached valves are not uncommon in the Corniferous Limestone, 

 but I have not seen a single perfect specimen. 



In general form, and in its surface-characters, Ccelospira concava (Hall) closely resembles 

 Leptoccelia flabellites (Conrad), and the two species have been usually regarded as belonging 

 to the same genus. According to Hall, however, C. concava possesses internal spires, which 

 are wanting in L. flabellites, thus necessitating the creation of a new genus for the former and 

 for some allied species. 



Locality and Formation. Corniferous Limestone, Port Colborne and Hagersville. 



Genus CENTRONELLA (Billings). 



" Shells having the general form of Terebratula. Dorsal valve with a loop consisting of 

 two riband-like lamellae, which extend about one-half the length of the shell. 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 backwards 

 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. This genus appears to stand 

 between Ttrebratula and JP aldheimia. 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 they are folded back ' : (Billings, 

 Canadian Journal, New Series, Vol. VI., p. 271, and Canadian Naturalist, Vol. IV., p. 131). 



Two species of this genus at least occur in the Corniferous Limestone ; but good speci- 

 mens are rarely to be procured, and I possess nothing more than detached valves, in which 

 none of the internal characters are exhibited. 



115. CENTRONELLA GLANS-FAGEA (Hall). 



Ehynchonella glans-fagea (Hall), Tenth Report on the State Cabinet, p. 125. 



Centronella glans-fagea (Billings), Canadian Journal, New Series, Vol. VI., Figs. 97, p. 

 271. 



Centronella glans-fagea (Hall), Sixteenth Report on the State Cabinet, p. 45, and Pal. 

 New York, Vol IV., Plate LXL, A. Figs. 1-21, 25, 26. _ 



Shell small, ovate or sub-rhomboidal, the greatest width about the middle, from which 

 point the sides slope to the beaks at an angle of about 85; front rounded ; valves very un 

 equal. Ventral valve considerably larger than the dorsal, convex, sub-carinate along th 



