1 50 [ Senate 



in the central and umbonal regions, compressed at the extremi- 

 ties ; area unknown. Surface ornamented by indistinct rounded 

 radiating strise, which are obsolete near the extremities ; of these 

 stride about twelve to fifteen may be counted near t]ie beaks, 

 but in passing towards the front they occasionally bifurcate^ 

 and others are implanted between, so that at the border the 

 whole number amounts to near thirty. Extremely fine and very 

 obscure concentric strise are also visible under a lens, on un- 

 worn parts of the shell. 



This little Chonetes has generally been referred to C. nana, which it 

 resembles yery nearly in size and form ; but it differs in averaging from 

 about ten to fifteen striae less than we usually see on that species ; the 

 striae are also much more depressed and rounded than those of C. nana. 

 Unfortunately none of the specimens I have seen give a clear idea of the 

 spines. I have as yet seen but two remaining bases of spines on each side 

 of the beak, though there may have been one or two more. The striae 

 usually bifurcate near the beak or on the upper half of the shell, so that 

 they appear at first view to be simple; and in some specimens there is no 

 bifurcation or interstitial addition of striae below the upper third of the 

 shell, so that it presents the aspect of a shell with simple rounded striae. 



Geological positio7i and locality. In the limestones of the aie of the 

 Hamilton group, associated with C. coronata and Tropidoleptus carinaius: 

 Devil's Bake-oven, Illinois. 



Chonetes setigera. 



Strophomena setigera, Hall : Geol. Rep. 4th Dist. N.T. 1843, p. 180. 



This species occurs in the Marcellus shale and Hamilton group of New- 

 York, in great numbers. It occurs in various states of preservation, some- 

 times extremely flattened in the thinly laminated dark shale, and more 

 convex in the calcareous portions of the group. The specimens preserve 

 from thirty-two to forty striae on the borders of the shell, and some indi- 

 viduals perhaps a few more. The cardinal tubular spines are nearly 

 vertical to the hinge-line, and in well preserved specimens are equal in 

 length to half the height of the shell or even longer. 



This species is often referred to Chonetes nana of de Yeeneuil, and 

 corresponds more nearly with that species than any other known to me in 

 the State of New- York. 



