102 BULLETIN OF THE 



crossed each other at right angles. For about half the width of the pectoral, 

 the suborbital passes directly outward, parallel with the pleural. From its 

 outermost point it goes to the orbito-nasal. The subrostral lies close to the 

 side of the prenasal, connects with the rostral, and does not reach the nasal 

 valve. The median is short. The prenasals are moderate, disconnected in 

 front. The pleural tubules of this surface, the lower, are most numerous on 

 the anterior section of the tube; they are not long, and have no branches. 



Myliobatis. 



Plates XI/VT.-XLVIII. 



Above the disk the canals and their branches extend only about half-way 

 from the vertebral line to the outer angles of the pectorals. Within these 

 limits the surface is closely occupied. There is a great tendency to form ro- 

 settes or mats of branchlets, at the ends of the tubules. From the forehead 

 back to the base of the tail on each side of the vertebral column, the groups 

 are dense, and so large as to be nearly continuous as a single one. The pleu- 

 rals range close to the borders of the branchial areas. 



On the lower surface the pleurals run outward and return near the anterior 

 border of the pectoral, and they then pass backward very near the basal carti- 

 lages, thus merely skirting the fin. Elongate tubules pass outward on the base 

 of the fin, hardly covering a fourth of the length, and others pass from the jugu- 

 lar extension inward upon the abdomen. In great part the orals are longitudinal. 

 A continuous tube has, in each of the species drawn, taken the place of the 

 separated sections of the oral, as apparent in the majority of the Batoidei. 



Myliobatis aquila (Plates XLVI., XLVIL). Tubules and branchlets are 

 numerous, above the abdomen, on both inner and outer sides of the laterals, 

 in this species. The scapular curves are not very prominent; the scapular 

 angle is sharp. A pre-scapular enclosure, of moderate size, lies in front of the 

 scapular, and, by union of pleural and the elongate post-scapular branch, a small 

 scapular area is enclosed. The branchial area is somewhat well covered by mats 

 of branchlets, from the occipital and from the pre-scapular tubules. The occipi- 

 tal is elongate, and in some cases it bears the occipital branch; in others, this 

 branch rises behind the aural. Tubules are very plentiful on the cranials. 

 The ante-orbital bend in these tubes is moderate, and their rostral portions are 

 short. Near the spiracle the orbital crosses the pleural, and it traverses two 

 thirds or more of the length of the snout before going to the lower surface. 

 In front of the eye the pleural rises upon the forehead; it makes its appear- 

 ance on the under side near the nostril. Pleurals, orbitals, and cranials are 

 thickly beset with tubules on or about the skull. 



Beneath the disk the outward course of the pleural lies near the anterior 

 margin, for two thirds of the length of the latter; the tube then turns back, 

 making a sharp angle, to take a backward course close to the jugular. It does 

 not extend as far back as to the pelvis, and the spaces enclosed by it, with the 

 jugular and suborbital, are very narrow and elongate. 



