80 
95. ATRYPA SPINOSA (Hall). 
Atrypa spinosa (Hall), Report 4th, Geol. Dist. New York, p. 200, Figs. 1 and 2. 
Atrypa dumosa (Hall), ibid, p. 271, Fig. 1. 
Atrypa spinosa (Hall), Pal. N.Y., Vol. IV., Pl. LITT. A., Figs. 1-14, 18, 24, 25. 
(Compare the Atrypa aspera or Atrypa reticularis, var, aspera of Dalman, Phillips, 
McCoy and Davidson. Compare also the Airypa squamosa of Sowerby.) 
This species in form and in all its general characters is identical with Atrypa reticularis® 
(Linn.), but its surface ornamentation is peculiar and distinctive. The surface is “ marked by 
strong, rounded, radiating coste, bifureating at unequal intervals, which are much stronger 
in the middle of the valve, and become obsolete or appear as gentle undulations towards the 
cardinal angles. In the middle of the valves there are about seven or eight of these costz in 
the space of half an inch. The shell is also marked by strong concentric lamellz, which are 
often about a line apart. In perfect shells these lamellz, at the crossings of the coste, are 
produced into tubular spines, which when worn off, leave the ordinary lamellose surface. 
The spaces between the lamellze are marked by fine thread like striz.” (Hall, Pal. N.Y., Vol. 
IV., p. 322). 
IT have only seen two specimens from the Corniferous Limestone exhibiting the above 
characters, but these are well marked. I agree with Hall in thinking that the characters of 
this shell are sufficiently distinct to entitle it to specific distinction ; but if it should prove, 
as is probable, to be identical with the Atrypa aspera of Kuropean authorities, the latter name 
has the priority. 
Locality and formation.—Rare in the Corniferous Limestone of Hagersville. 
Genus SPIRIFERA (Sowerby). 
Shell-structure fibrous and impunctate ; form very variable, but typically more or less three- 
sided or quadrate, sometimes oval or sub-circular. Hinge-line straight, mostly as long as or 
longer than the greatest width of the shell, sometimes shorter. The cardinal angles some- 
times obtusely rounded, more commonly produced or extended, sometimes greatly so. Sur- 
face usually with radiating ribs, or smooth, or striated. Generally an elevated fold in one 
valve and a corresponding sinus on the other. Valves articulated by teeth and sockets; the 
ventral valve the larger, with a more or less prominent beak, a well-marked area, and a tri- 
‘angular foramen which is sometimes closed by a pseudo-deltidium. Dorsal valve with a 
narrow area and a wide triangular foramen. Interior more or less occupied by two spirally- 
rolled lamelle, forming two cones, the apices of which are directed towards the cardinal 
angles. 
gee large number of species of Spirifera have been described from the Devonian Rocks of 
North America. With the exception, however, of the extraordinarily abundant S. mucronata, 
our collections of the species of this genus are very imperfect. I have only been able to 
satisfactorily identify S. varicosa, S. duodenaria, 8. raricosta, S. fimbriata, and S. mucronata, 
—the last from the Hamilton group, and the others from the Corniferous Limestone. 
> 
96. SPIRIFERA MUCRONATA (Conrad). 
Delthyris mucronata (Conrad), Ann. Report on the Geology of New York, p. 54. 
Delthyris mucronate (Hall), Geol. Report, 4th District New York, p. 198. 
Spirifera mucronata (Billings), Canadian Journal, New Series, Vol. VI., p. 254, figs. 59- 
62. | 
Shell semi-circular or semi-oval, usually sub-trigonal or triangular, the cardinal angles- 
sometimes truncated, but more commonly acute and extended, often produced into long mu- 
cronate extensions. In a few instances, the hinge-line is very little longer than the greatest 
width 6f the shell below, but it is generally twice or thrice the length of the shell measured 
from the beak to the front margin, and occasionally four, five, or six times as great. The 
sides of the shell are straight, or curved slightly, and the front margin is straight or concave. 
The ventral valve is more convex than the dorsal, though sometimes only slightly so, 
with a small incurved beak, and a narrow linear area, the height of which, when most 
