83 , 
with a minute beak and a rounded, mesial fold, and a narrow sub-linear area. Plications 
obscure, becoming obsolete towards the cardinal angles, and dying away in the neighbourhood 
of the hinge-line. Surface marked with shallow concentric furrows separated by interspaces 
which are studded with elongated tubercles. There are from three to four or more furrows 
in the space of two lines, and from five to eight elongated tubercles in the space of one line 
transversely. In casts of the exterior, the elongated tubercles are represented by narrow 
elongated pits arranged in concentric bands. 
Spirifera fimbriata not uncommonly attains a width ofan inch and three quarters by a 
length of thirteen lines, but average examples are smaller than this. It is readily recognised 
by its comparatively short hinge-line, its rounded cardinal angles, its obscure plication, and 
its surface ornamentation. 
Locality and Formation.—Corniferous Limestone of Port Colborne. Also, according to 
Mr. Billings, in the Hamilton Shales of Bosanquet. 
Genus CYRTINA (Davidson). 
Shell small and resembling that of Spirifera in its general form. Shell-structure pune- 
tate. Valves very unequal; the ventral valve elevated and pyramidal in shape; the area very 
high, with a long narrow foramen, closed by a pseudo-deltidium ; the dental lamell conyerg- 
ing from the margins of the foramen, and uniting to form a mesial plate or septum, which 
divides the cavity of the ventral valve into two compartments. Dorsal valve nearly flat or 
moderately convex. Spires well-developed, and resembling those of Spirifera and Spiri- 
Serina. 
The genus Cyrtina is closely allied to Cyrtia {Dalman), and Spiriferina (D’Orbigny), and 
has also near relationship with the genus Spirifera. Two species have been recorded by Mr. 
Billings, as occurring in the Devonian Rocks of Western Ontario, namely Cyrtina rostrata 
(Hall), from the Corniferous Limestone, and C. Hamiltonensis (Hall), from the Hamilton group. 
The latter is a common species, but the few examples of Cyrtina, which I have seen from the 
Corniferous Limestone are too imperfect to admit of specific determination. 
101. CyRTINA.HAMILTONENSIS (Hall). 
Cyrtia Humiltonensis (Hall), Tenth Report on the State Cabinet, p. 166. 
Cyrtia Hamiltonensis (Billings), Canadian Journal, New Series, Vol. VI., p. 262. Figs. 
80-82. 
Cyrtina Hamiltonensis (Hall), Pal. New York, Vol. 1V., p. 268. Plate XXVIT., Figs. 1-4, 
and Plate XLIV., Figs. 26-33, and 38-52. 
“Shell more or less triangular or sub-pyramidal ; hinge-line equal to the greatest width of 
the shell; proportions of length, breadth, and height variable, but frequently the width is 
equal to the length of the ventral valve, and the height of area is equal to the length of the 
dorsal valve; surface plicate. Ventral valve quadrilateral in outline, obliquely sub-pyramidal, 
most prominent at the beak, which is very variable in elevation and straight or a little arched 
over the area, and not unfrequently attenuate and distorted or turned to one side ; mesial 
sinus wide and strongly defined, rounded or sub-angular in the bottom ; area variable, large 
and elevated, plane or arcuate in different degrees, with the lateral margins angular, dis- 
tinetly striate in both directions ; fissure narrow, closed by a convex pseudo-deltidium, which 
is perforated above by an oval or narrowly ovate foramen. Dorsal valve depressed, convex, 
with a broad, more or less prominent mesial fold, which is bounded by broader furrows than 
those between the plications, and is sometimes extremely elevated in front ; the beak scarcely 
rising above the hinge-line ; area narrow, linear, but quite distinct ; surface marked by about 
six to eight (rarely one or two more) simple rounded plications on either side of the mesial 
fold and sinus, and these are crossed by very fine concentric lines of growth, which at intervals 
became crowded and sub-imbricate, especially towards the margins of older shells. The finer 
surface-marking is minutely granulose or papillose, and the shell-structure is distinetly 
punctate. In some of the larger individuals there is an obscure elevation on each slope of 
the sinus, resembling an obsolete plication. The longitudinal median septum extends for 
more than half the length of the ventral valve, and is continued into the cavity beneath the 
pseudo-deltidium. These features are shown in casts and in transverse sections of the valve. 
