PLATE 54. 



Pelvis of PLATOSOMIA. 



Fig. 1. PoT.\MOTRYGON ciRCULARis. M. C. Z. 296 (Page 419). 



Fig. 2. DiscEus^THAYERi. M. C. Z. 606 (Page 426). 



Fig. 3. Myliobatis freminvillii. M. C. Z. 1160 (Page 432). 



Fig. 4. Aetobatus narinari. M. C. Z. 389 (Page 441). 



Fig. 5. Rhinoptera jussieui. M. C. Z. 863 (Page 447). 



Fig. 6. MoBULA HYPOSTOMA. M. C. Z. 683 (Page 453). 



The figures on this plate are from a group of the Platosomia characterized by a median process in 

 front of the pelvis, among other features. The process is shortest in the Myliobatidae, fig. 3-4, longer in 

 the Mobulidae, fig. 6 and longest in the Potamotrygonidae. Its presence has no bearing on a question 

 of affinity with Dipnoi, Plate 52, fig. 4-7. 



