72 
Orthis Livia is an exceedingly elegant species, and can usually be recognised without any 
difficulty. It is allied to O. Vunuaemi, (Hall), but is a larger form, and is more coarsely 
ribbed. 
Locality and Formation.—Corniferous Limestone of Port Colborne, and Lot 6, Con. 1, 
Wainfleet. 
85. Orrais VANUXEMI (Hall). 
Orthis Vanuxemi (all), Tenth Report on the State Cabinet, p. 136. 
» Orthis Vanuxemi (Billings), Canadian Journal, New Series, Vol. V., p. 269, figs. 17, 
18, 19. ; 
Orthis Vanuxemi (Hall), Pal, N.Y., Vol. IV. Plate VL, fig. 3. 
Shell very nearly circular, compressed and flattened; hinge-line very short, rounded. 
Dorsal valve gently and regularly convex; the beak hardly prominent, not incurved ; the 
area narrow and linear. Ventral valve with its greatest convexity in the neighbourhood of 
the beak, nearly flat, or commonly slightly concave towards the front; the beak small, but 
more prominent than that of the dorsal valve, somewhat arched. Area narrow and curved, 
about one-third wider than the area of the dorsal valve. Foramen comparatively large, wider 
than high, triangular. Surface covered with close-set, fine, elevated striz#, which increase 
both by bifurcation and interstitial addition, and which are indistinctly cancellated by concen- 
tric strize. About five strize in the space of a line, but more in the neighbourhood of the 
beaks. Entire surface minutely punctate ; a few concentric, imbricating lines of growth. 
As regards the characters of the interior, ‘‘ the dorsal valve shows a strong cardinal process, 
which is continued in a prominent rounded median ridge for half the length of the shell, where 
it sometimes divides, or gradually becomes obsolete ; there are sometimes visible low trans- 
verse ridges, which divide the muscular impression. The crural processes are prominent, and 
sustained below by strong oblique ridges. In the interior of young specimens, the marks of 
the external striz are visible nearly or quite to the muscular impression; while in older speci- 
mens these marks extend little beyond the margin. The interior of the ventral valve is marked 
by a large flabelliform muscular impression, which reaches from one-half to two thirds the 
length of the shell. The central or adductor impression is sometimes simple, and sometimes 
longitudinally divided by aslight median ridge, which is stronger below. In the older shells 
the ovarian spaces are pustulo-e. The dental lamellz are strong and divergent, supported 
below by the ridge which margins the muscular impression. Vascular impressions are rarely 
seen extending beyond the muscular area, Under a lens, the interior surface is distinctly 
punctate. In all well-preserved specimens the exterior shows minute tubular openings in the 
striz ; and when the striz are much worn, these also are to be seen to be tubular, while a 
farther wearing of the surface shows more distinctly the minute punctate character of the 
shell.”’ —( Hall, Pal. N.Y., vol. iv., p. 47.) 
Orthis Vanuremi is one of the most characteristic of the Brachiopods of the Hamilton 
Formation, and though not particularly abundant in Western Ontario, it is a yery com- 
mon species in the State of New York. It is distinguished from O. Livia by its finer striation 
and its more circular form. It is also a smaller species, average specimens having a width of 
about thirteen lines, and a length of about eleven lines and a half, though examples both 
smaller and larger than this are not uncommon. Small specimens are not at all unlike the Orthis 
hybrida (Sowerby), of the Silurian Rocks of Europe and North America. There is, also, 
considerable doubt as to whether the O. lewcosia and 0. Penelope of Hall, from the Hamilton 
group of the State of New York, can beregarded as more than mere varieties of 0. Vanuaxemi. 
Locality and formation.—Hamilton group of Widder and Bartlett’s Mills, near Arkona, 
in the Township of Bosanquet. Also at Canandaigua and at various other localities in the 
Hamilton Formation of the State of New York. 
& Genus CHONETES (Fischer). 
Shell semi-oval or transversely oblong, with a wide straight hinge-line. External margin 
of the area of the ventral valve furnished with a row of tubular spines. Surface radiately 
striated, often spinose. foramen in the ventral area distinct, but partially closed by a pseudo- 
deltidium. Valves articulated by teeth. Dorsal valve with a cardinal process which is simple 
at the base, but bifid or grooved at the extremity. Interior of the shell pustulose or papillose. 
