FOSSILS OF THE NIAGARA GROUP. 3 51 



11. DESCRIPTIONS OF FOSSILS OF THE NIAGARA GROUP. 



ECHINODERMATA. 



In the Report of Progress of the Geological Survey of Wisconsin for I860,* 

 I described several species of Crinoidea, two Cystideans, several species 

 of Brachiopoda, Gasteropoda and Cephalopoda, from the limestones of 

 Racine and Waukesha ; leaving a considerable number of species unde- 

 scribed for want of satisfactory material. It has not been in my power 

 to make such collections as I then anticipated ; and the following descrip- 

 tions relate almost exclusively to species that have been in my cabinet 

 for several years, and which were studied, and many of them determined, 

 at the time of making the report above cited. 



Some of the Crinoidea are very interesting ; but the Cystideans possess 

 a peculiar interest, as offering forms which, so far as I know, have not 

 been discovered in any other localities. The specimens, with few excep- 

 tions, are casts of the interior of the test, or impressions of the exterior 

 left in the matrix. A few of the species retain the plates to such an 

 extent that the structure can be determined. Since it appears probable 

 that we shall, for some time at least, be dependent upon similar imperfect 

 materials for our knowledge of these fossils, I shall endeavor to give 

 such descriptions as will enable the student to recognize the species, with 

 the hope that some of them at least will be illustrated at a future period. 



GENUS GOMPHOCYSTITES, n. g. 



[yO|U^ocr, clavus ; Kvarocr, vesica.1 



Body elongate pyriform, very narrow at the base, gradually enlarging 

 above, and inflated near the upper extremity. Surface composed of 

 numerous series of polygonal plates which have a spiral arrange- 

 ment. Apertures upon the upper surface, one of them being 

 subcentral, and the other a little eccentric. • Arms sessile, lying in 

 grooves excavated in the surface of the plates, originating near the 



* Report of the Superintendent oj the Geological Survey, Legislative Documents, 1861 . ' 



