PLATE 68. 



RAIIDAE. 



Fig. 1. Raia erinacea. M. C. Z. 358 (Page 337). Fig. 2. Uraptera agassizii. M. C. Z. 

 549, (Page 367). Fig. 3-4. Sympterygia acuta. M. C. Z. 632 (Page 370). 



The proterygial basalia of the pectoral fins of the Narcaciontidae have numerous joints between the 

 antorbital, ao, and the pectoral arch, pel; the Raiidae have comparatively few, most often but a single 

 one, that is two segments in the pectoral base opposite the gills, an arrangement gaining in firmness of 

 the disk along the sides of the branchial chamber. Marked variations occur among the genera of Raiidae. 

 In Sympterygia, fig. 3 a semicartilaginous mass in front of the skull displaces the rostral cartilage; in 

 IMalacorhina the rostral cartilage is lacking and the forward part of the skull is much like that of the 

 Dasybatidae. In general the hyobranchials are reduced, but the copula, hbr', is complete and not 

 segmented as in Dasybatidae nor divided as in Narcaciontidae. The scapular, sc, overlaps the girdle. 

 The prominent lateral prepelvic processes recall similar ones on the fossil genus Cyclobatis. 



