i!»^ Description of new Palceosoic Fishes. 



Exposed portion wholly covered with fine longitudinal ribs, which are 

 highly ornamented by closely approximated transverse lines. Pectination 

 finest on middle and lower portion of sides. 



Another spine of Otenacanthus has been found in the same 

 stratum and place with that now described, but it is quite 

 different. A figure and description of this {C. vetustus, N.) 

 are given in Vol. I, Part II, p. 326, PI. 35, Fig. 3, of the 

 Report of the Geological Survey of Ohio ; and by reference 

 to these it will be seen that the spine before us is very much 

 more compressed, and is ornamented by more numerous and 

 finer longitudinal ridges on the sides. 



From the Huron Shale, Sheffield, Loraine Co., Ohio. 



Found by Mr. Jay. Terrell. 



Khykciiodus occidentalts, (n, sp.) 



Teeth of small size, much compressed. Anterior margin slightly curved 

 but nearly vertical. Superior margin gently arched downward from the 

 prominent anterior point, forming a much compressed triturating surface or 

 edge. Posterior portion of upper margin acute-edged. Exterior lateral sur- 

 face striated obliquely backward. Basal margin formed by the edges of 

 external and internal laminae, of which the edges are broken and irregular. 



From the Hamilton Limestone, Waverly, Iowa. 



Rhynchodits excavatus, JSTewb. 



R. excavatus, iV"., Geol. Survey of Wisconsin, Vol. %'p. 390. 



Tooth small ; size, when entire, perhaps two and a half inches long 

 by one and a quarter deep ; the crown alone preserved. Of this, the 

 external surface is marked vertically .with vermicular furrows ; superior 

 margin sinuous, terminating anteriorly in, a pimuiherit. point ; the superior 

 surface irregularly excavated and roughened, showing two prominent points 

 or tubercles, one on the middle of the exterior-margin and one near the ante- . 

 rior extremity. The inner surface of tlie'tootlf shows a prominent ridge run- 

 ning up to the anterior point. 



This tooth is evidently fitted for trituration rather than cut- 

 ting, and resembles in its general form M. franrjens" of the 

 Corniferous limestone. It is, however, much smaller and thin- 

 ner ; and the tubercles of the upper surface are differently 

 situated than in that species. 



Hamilton Group, Brown Deer, Milwaukee Co., Wisconsin. 



Collected by Prof. T. C. Chamberlain. 



