420 



Description of a new Trilohite. 



4000000 years, and the rate of subsidence would then be one 

 foot in 100 years. We know the levelling power of running 

 water. Any small fold that could have been produced by the 

 subsidence of ten feet in the first thousand vears would be cer- 

 tainly obliterated by the current of the next ten years. The 

 same would be the result for the second 1000 years and so on to 

 the end, at which time the bottom of the ocean would be quite 

 level. E. B. 



ARTICLE L — Description of a new Trilohite f win the Potsdam 

 Sandstone ; by Frank H. Bradley, with a note by E. 

 Billings. 



{Extracted from Silliman^s Journal, 2nd Series, Vol. 30, page 241, Sep- 

 tember, 1860. 



[Read before the Am. Assoc, for the Advancement of Science, at Newport.] 



CONOCEPHALITES MINUTUS, (u. Sp.) 

 1 

 "^ 2 o 



Fig. 1. The head magnified. The dotted lines represent the supposed 

 outlines of the parts not preserved. 

 Fig, 2. The pygidium magnified. 

 Fig. 3. A detached cheek, magnified. 



Cephalic shield apparently semi-circular, or nearly so ; anterior 

 margin as far as preserved with a narrow slightly elevated 

 rim, just within which there is a rather strong groove. Glabella 

 conical, slightly narrowed at the neck segment, three-fourths the 

 whole length of the head, very convex and obtusely carinated 

 along the median line. Neck segment rounded and prominent ^ 

 neck farrow narrow, but well defined. There are two pairs o 

 deep glabellar furrows which are inclined inwards and backwards 

 at an angle of about 45° ; their inner extremities distant from 

 each other rather more than one-third the width of the glabella. 

 The anterior lobe is a little less than one-half the whole length of 

 the glabella, excluding the neck segment; the two posterior pairs 



