244 D=* 



Smaller: rods larger and less oblique; edge undulate 



and serrate P. perniciosus. 



Larger : rods smaller and more oblique ; edge entire or 



irregular P. gladius. 



Pelecopteeus perniciosus, Cope. 



Although the pectoral spines of this fish are abundant, they are rarely 

 obtained unbroken ; and I had long been familiar with their basal and distal 

 portions before I was aware that they bore that relation to each other. The 

 finest example was obtained by my friend Professor Merrill, on Spring 

 Creek, in Rooks County. It includes spines and clavicles of both sides, with 

 scapular and basilar bones of one side. Neither spine is complete, but the 

 longest measures twenty-eight inches in length. The component rods make 

 a small angle with the cutting-edge, and, commencing narrow at the base, 

 widen out at the middle, and retain their width to the end at the cutting- 

 border. The rods at the back of the spine are narrower than those at the 

 middle and edge. The section is narrow, especially at the back, and it is- 

 thickest a little within the edge. There are thirty-four rods at the base, and 

 fourteen at the middle of the spine. 



At the base, the cutting-edge is almost straight, but it soon becomes 

 undulate. Before the middle is reached, the convexities become low teeth, 

 and from this point to the end the teeth arc pronounced. They are acute in 

 apex and edge, and have a long anterior and short posterior border. Each 

 1ooth marks the end of one of the oblique component rods. The apex of 

 each tooth is the end of a transverse thickening or low ridge of the surface 

 of the spine, so that the culting-edire is equally acute at the bottoms of the 

 concavities as at the rather obtuse unices of the teeth. The cement oj 

 enamel layer extends, on both sides of the spine, 0.7o inch from the cutting 

 edge; it is composed of small, aggregated tubercles. In" this specimen, the 

 scapula is lighter than in the species next described, and has its outer anterior 

 angle drawn out into a slender process, which does not exist in the latter. 

 In this specimen, the fan-shaped inferior process of the scapula is present. 



Measurements. 



M. 



Length of the clavicle round its curve (proximal cud broken) 0. S15 



Width of the clavicle near the lower end 0.043 



Vertical diameter of the scapula 0. 105 



