OS BULLETIN OF THE 



are at least suggestive of closer affinities in the distant past. These are brought 

 prominently forward in comparisons of such tubes as the medians and sub- 

 orbitals of the two forms. 



Pristis. 



Posteriorly the laterals of Pristis pectinatus (Plate XXIII.) are straight. 

 On the. tail there is a slight downward tendency, and the canals end near its 

 extremity, at the lower edge of the muscles. Anteriorly, above the thoracic 

 region, they are drawn toward each other; at the shoulder each makes an out- 

 ward bend, from which the scapular and the post-scapular branches extend. 

 A comparatively small area is enclosed by the pleural ; from the shoulder the 

 tube runs out and backward, then it turns forward, along the inner edge of 

 the pectoral fin, to meet some of the tubules from the orbital, near the hinder 

 part of the orbit, after which it makes a sharp bend and goes back a short dis- 

 tance parallel with its former course before passing down the side to the lower 

 aspect, about opposite the aural. One or two post-scapular branches, together 

 with the posterior pleural tubules, form a network of branchlets on the pectoral. 

 Lateral, pleural, and suborbital possess slender tubules. Similar ones on the 

 rostral have delicate branchlets. 



On the ventral surface the pleurals run toward the gill openings, in front 

 of which, about one third of the distance to the mouth, they meet the jugulars. 

 The space included by these tubes is small. 



The aural is deeply bent backward. A short occipital connects it with the 

 orbital. The latter goes close below the eye and in front of it, about half a 

 diameter, passes to the loAver surface around the edge. Near the fontanelle 

 the cranials diverge slightly, making a shallow bend; near the end of the ros- 

 trum they converge, but diverge again at the tip; in general, their course is 

 tolerably direct. These, as the other tubes of this surface, are beset with a 

 great many very fine short tubules. 



Angular and jugular are moderate. The orbito-nasal is short; in front it 

 meets the suborbital and the subrostral. Only a small portion ot the sub- 

 orbital is to be seen from below. The subrostral is much elongated, has a 

 waved course, and is bent prominently forward in front of the nostril. The 

 nasal is transverse, and waved in outline. The median is longitudinal and 

 short. From it the prenasals turn abruptly outward, toward the nostrils, be- 

 fore taking a course of tolerable directness toward the rostral extremity. Close 

 to the latter they appear as if crowded back, so as to make a fold directed 

 toward the median line. Behind each side of the mouth there is a discon- 

 nected oral ; toward the middle the tube bends forward, at the outer end it is 

 turned back in a hook. 



Although there is much resemblance between the majority of the canals 

 of Pristis and those of Pristiophtirus, the presence of the pleural and the 

 scapular branches fixes the position of the former in the Batoidei. 



