80 



95. ATRYPA SPINOSA (Hall). 



Atrypa spinosa (Hall), Report 4th, Gool. Dist. New York, p. 200, Figs. I and 2. 

 Atrypa dumosa (Hall), ibid, p. 271, Fig. 1. 



Atrijpa spinosa (Hall), Pal. N.Y., Vol. IV., PI. LIII. A., Figs. 1-14, 18, 24, 25. 

 (Compare the Atrypa asper,i or Atrypa rcticularis, var, aspera of Dalman, Phillips, 

 McCoy and Davidson. Compare also the Atrypa 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 costse, bifurcating 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 costse in 

 the space of half an inch. The shell is also marked by strong concentric lamellge, which are 

 often about a line apart. In perfect shells these lamellae, at the crossings of the costse, are 

 produced into tubular spines, which when worn off, leave the ordinary lamellose surface. 

 The spaces between the lamellae are marked by fine thread like striae." (Hall, Pal. N.Y., Vol. 

 IV., p. 322). 



I 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 European 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 lamellae, forming two cones, the apices of which are directed towards the cardinal 

 angles. 



A 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*?, varicosa, S duodenaria, V. rarico4a, S. fimbriata, and S. mucronata, 

 the last from the Hamilton group, and the others from the Corniferous Limestone. 



96. SPIRIFERA MUCRONATA (Conrad). 



DeltJiyris mucronata (Conrad), Ann. Report on the Geology of New York, p. 54. 

 Ddthyris mucronata (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 of 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 



