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, 
Pape ¥.. Vol. LV; ped 28): 
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. CaLosprra concava (Hall). 
Leptocelia concava (Hall), Pal. N. Y., Vol. IIL, p. 245, Pl. XXXVIIL., Figs, 1-7. 
Leptocelia concava (Billings), Canadian Journal, New Series, Vol. VI., p. 352, Fig. 127. 
Celospira concava (Hall), Sixteenth Report on the State Cabinet, p. 60. 
Ceelospira concava (Hall), Pal. N. Y., Vol. IV., Pl. LIII., Figs. 13-19. 
Shell small, ovate, or sub-orbicular, the width being’ equal to or a little less than the 
length. Ventral valve convex, elevated along the middle, the beak small and incurvyed. 
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 ocea- 
sionally bifurcate. 
According to Hall, the dorsai 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, Cwlospira concava (Hall) closely resembles 
Leptocelia 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 Zerebratula. Dorsal valve with a loop consisting of 
two riband-like lamella, 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 Tvrebratula and 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 laminze 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 1 possess nothing more than detached valves, in which 
none of the internal characters are exhibited. 
115. CENTRONELLA GLANS-FAGEA (Hall). 
Rhynchonella 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 LXI., 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 Jarger than the dorsal, convex, sub-carinate along th 
