PLATE 74, 



RHINOPTERIDAE. 



Fig. 1-2. Rhinoptera jussieui. M. C. Z. 863 (Page 447). 



The skull of the Rhinopteridae is short, broad, and somewhat indented in front. The cephalic fins 

 are quite distinct from the pectorals, are situated at a lower level, and are not widely separated from one 

 another in front of the mouth. The mouth is widened and the jaws are broadened, the narial cartilages 

 are long and broad. The propterygial bases of the pectorals are unsegmented at the sides of the gill 

 chambers, unless it be in very young stages, they are enlarged and strengthened, and to further conduce 

 to stability and firmness the lateral stays, h, bra, bre, are so greatly modified as to be hardly recognizable 

 as gill rays; the anterior, Is, is directed forward over the antorbital, ao, as a single elongate cartilage; 

 the second, brr, fig. 1, is directed outward, segmented and turned back in its outer segment; the third, 

 bra, and the following show the outer segment firmly attached to the base of the pectoral while the inner 

 segment of the ray, bre, is broadened and enlarged into a sort of hammer-shape, solidly attached to the 

 ceratobranchial and the epibranchial at their junction, and also to the outer stay or segment, bra. The 

 epitropeal cartilages, supratropeal and subtropeal, evs, form regular series above the arches, and irregular 

 ones below them. The extrabranchials, sbr, supra and sub are large. The mcsopterygia are much 

 reduced or fused with the girdle, pet. The anterior hm, in fig. 1, should be sp. Changes in the 

 structure of the gills leading towards Mobula are seen in the Rhinopteridae; the inward section of each 

 lamina takes on more of the functions of protection and of propelling the food toward the stomach while 

 the outer section is more concerned in purifying the blood, see Plate 59, fig. 9-10. 



