116 Wisconsin Academy of Sciences^ Arts^ and Letters. 



cement are found mucb. larger and in a more perfect condition than 

 those pictured and described in reports o£ previous geological sur- 

 veys. A magnificent and perfect Pleurotomaria perlata five inches 

 in diameter, found in the Niagara shale, and also in the Guelph 

 or Gault, a Trochoceras, Gehhardii, six inches in diameter, from the 

 cement rocks, besides many others, claim honorable mention. Iq 

 no other place are such unique lamellibranchiata to be found, 

 particularly the Moceraunas and Amphicelia^ Amhonychia, and 

 Paleocardia. I have quite a number of perfect specimens, retain- 

 ing the whole or parts of their beautiful striated shells. 



It is in Schoonmaker's Quarry that several distinct species of 

 trilobites belong which are not found elsewhere — in any fossilifer- 

 ous formation. 



Prof. J. Hall, in his description of the fauna of Wisconsin, was 

 often obliged to make use of imperfect material, and in resorting 

 to the very unsatisfactory mode of delineating restored parts, or 

 "supposed differences," he would naturally be much disappointed 

 and mortified to find his opinions erroneous upon the subsequent 

 discovery of perfect specimens, which were heretofore entirely 

 new, or but little known. On this account it is questionable 

 whether Hall's synonyms for fossils like the lllamus, Sphcerexo- 

 chus, Phragmoceras, et cetera, when perfect specimens prove them 

 to be so radically different from Hall's descriptions, should be 

 " saddled " with the names he intended should be applied to them, 

 especially when his opinions are based upon a smgie part or frag- 

 ment of a perfect specimen, and also when the synonym is foreign 

 to the idea suggestive of its character. For example, the pygidium 

 of the Illoenus cuniculus is confounded with the Bridgeport and 

 Waukesha Ilkenus armatus, which is probably an adult sjDeci- 

 men of Illoenus insignis, or lllcenus Worthmanus of Winchell, or 

 Illoenus Spring fieldensis^ of Meek. There are other species of 

 the Illoenus^ or Asaphus^ to which the glabella has a slight re- 

 semblance to Hall's description, but otherwise are totally different. 



The pygidium of Hall's Sphoereocochus Romingeri is simply a 

 mutilated specimen of a pygidium of S. mirus of Beyrich. I 

 am induced to make these assertions after a careful comparison 

 with perfect specimens in my cabinet. Allow me, also, to state 



