BUFFALO SOCIETY OF NATURAL SCIENCES 93 



that there is considerable difference in the size and character of the 

 tubercles among the species of one genus; in fact, one species may 

 have tubercles and another not, as is seen in the genus Dinichthys. 

 It therefore seems proper to refer the present specimens to A sptdichthys, 

 merely extending the definition of this genus so as to include forms 

 with denticles of the same kind, but of somewhat smaller size. 



The following specimens are all from the Conodont bed (Genesee) ; 

 Eighteen Mile Creek, near North Evan's, Erie County, New York. 

 Collected by W. L. Bryant. 



E 1970 Right antero-ventrolateral lacking anterior portion (PI. 25). 

 The posterior tip is restored from a squeeze taken from 

 the impression in the matrix. The plate as far as pre- 

 served, is 22 cm. in length, and 11 cm. in maximum 

 width. The ornamentation consists of large, smooth, 

 rounded tubercles, somewhat unequal in size and some of 

 them slightly stellate at the base; a portion of the inner 

 border of the plate is smooth, without denticles. The 

 plate is practically uniform in thickness throughout and 

 the under side is almost smooth, showing no striae. 



E 1971 An imperfect plate, probably a ventral, with its impression 

 in matrix. Its ornamentation resembles that of the pre- 

 ceding specimen, except that in places the tubercles are 

 somewhat more crowded. (PI. 26, fig. 2.) 



E 1972 Fragmentary plate. 



E 2399 Impression of the front half of an antero-ventromedian and 

 a plaster cast made from it (PL 26, fig. i). This plate 

 differs from all other antero-ventromedians yet described. 

 Its characters are clearly brought out in the illustration. 

 Along the front margin as well as on either side it has a 

 broad flange for overlap by the other plates of the plastron. 

 From the fact that it narrows but little posteriorly, it 

 would appear to have been squared off more or less pos- 

 teriorly, instead of ending in an acute point, as is the case 

 in the species of Dinichthys in which the antero-ventro- 

 median is a distinct plate. On the visceral surface the an- 

 terior margin is strengthened by a low ridge, and, rimning 

 backward from this, in the median line, there is another 

 low, rounded ridge very much as in Dinichthys, 



This specimen was collected by Prof. C. J. Sarle. 



