BUFFALO SOCIETY OF NATURAL SCIENCES 167 



from about the middle for a considerable distance beyond in the direction of the 

 apex. The form of the cross-section leaves no doubt that both spines present 

 the same aspect, presumably the outer or external face. On the opposite, or in- 

 ternal face, the median carina appears to be gently rounded throughout its entire 

 length. One of the distinguishing characteristics of this species, however, is that 

 the axial ridge on the side which is presumed to be external remains sharply 

 triangular only in the distal half of the spine, becoming widened into a broad flat 

 elevation, smooth or but faintly striated, and nearly rectangular in cross-section, 

 toward the base of the spine. The general surface is smooth, save for the usual 

 delicate striae, slightly convergent toward the apex, and possibly of the same 

 nature as growth lines. 



The foregoing description is, however, incorrect in one particular. 

 The spines do not both present the same aspect. It is plain from 

 the conformation of the median ridges and from the curvature of the 

 two spines as they appear side by side, that one presents the inner, 

 and the other the outer aspect. The median ridge of one is trian- 

 gular in cross-section, while in the other it is flat. 



The following specimen from the Conodont bed apparently also 

 belongs to this species. If the determination is correct it extends the 

 range of the species from the Lower Hamilton (Mid. Devonic) into 

 the Lower Genesee (U. Devonic). 



E 1906 Fragment of a spine having a cross-section somewhat similar 

 to that of M. long(Bvus. 



Machaeracanthus peracutus Newberry 



(PL 53, %. 3) 



The following specimens, which are smaller and more slender than 

 examples of M. major probably belong to M. peracutus Newberry. 



E 1850 Distal half of spine, in matrix. (PI. 53, fig. 3). 



Onondaga limestone; Cemetery Quarry, Buffalo, New 

 York. Collected by Mr. F. K. Mixer. 



E 1851 Incomplete spine. 



Onondaga limestone; Cement Quarry, Buffalo, New 

 York. Collected by Mr. F. K. Mixer. 



E 1852 Spine of a young individual. In the smaller spines of this 

 species, the longitudinal axis of what we here call the 

 under side, is relatively higher than in those of adults. 

 Other data same as preceding. 



