PLATE 69. 



RAIIDAE and DASYBATIDAE. 



Fig. 1-2. Malacorhina mira. M. C. Z. 226 (Page 372). Fig. 3. Urotrygon aspidurus. 

 M. C. Z. 555 (Page 405). Fig. 4-5. Urobatis sloani (Page 402). 



A peculiarity of Malacorhina is the absence of a rostral cartilage, the front of the skull in consequence 

 resembling that of Dasybatus. The scapular attachment overlaps the girdle as in the other Raiidae. 

 A feature not noticed in the others is a small movable cartilage, x, resting above the base of the sus- 

 pen.sorium, a rudiment perhaps of a sometime complete arch which included the spiracular cartilages and 

 the pterygoquadrates, the upper jaws. The copula is unsegmented and the joints in tlie bases of the 

 pectorals oppo.iite the gills are like those of the family in general. 



Urotrygon, fig. 3, and Urobatis, fig. 4-5, agree in most respects with other Dasybatidae; they have 

 no rostral cartilage, there is no joint in the pectoral base opposite the gills anfl the scapular articulations 

 are against the ends of the scapula, .sc. not above the girdle as in the Raiidae. Urotrygon, fig. 3, appar- 

 ently lacks the median segment of the copula, as in the Torpedoes. In Urobatis there is a slender 

 elongate supraspiracular cartilage. 



