PLATE 56. 



ANTERIOR VERTEBRAE. 



Fig. 1. Callorhynchus TRiTORis. M.C. Z. 173. Fig. 2. Chimaera monstro.sa. M.C. Z. 326. 

 Fig. 3. Pristis microdon. M. C. Z. 302 (Page 26.5). Fig, 4. Rhinobatus percellens. M. C. Z. 

 430 (P.ago 278). Fig. 5. R.\ia erinacea. M. C. Z. 358 (Page 337). Fig. 6. Pot.\motrygon lati- 

 CEPS. M. C. Z. 290 (Page 417). Fig. 7. Taeniura ly.mma. M. C. Z. 620 (Page 399). Fig. 8. 

 Myliobatis californicos. M. C. Z. 636 (Page 429). Fig. 9. Aetobatus n.'Uiinari. M. C. Z. 677 

 (Page 441). Fig. 10. Rhinoptera jussiedi. M. C. Z. 863 (Page 447). 



Figure.s 1 and 2 show the condition of the vertebrae in the Chi.smopnea, how few of them are in- 

 cluded in the consoHdation, the articulation of the erectile spine, and the condition of the notochord, 

 without rings in Callorhynchus, fig. 1, with rings in Chimaera, fig. 2. Figures 3-10 are from among the 

 lowest to the highest of the Platosomia. They indicate the gradually increasing number of the vertebrae 

 taking part in the anchylosis, with the decrease in size and withdrawal backward of tlie lateral wings or 

 stays so prominent in the Pristidae, fig. 3, the scapulary attachment of the shoulder girdle superior in 

 Pristidae and Rhinobatidae, fig. 3-4, inferior in the Raiae, fig. 5, and a lateral articulation in Dasybatidae, 

 fig. 7, Potamotrygonidae, fig. 6, Myliob.atidae, fig. 8, Rhinopteridae, fig. 10 and the Mobulidae. The 

 different styles of attachment of the .shoulder girdle apparently divide the Platosomia into groups. A 

 considerable increase in irregularity of vertebrae and processes obtains as the most specialized 

 genera are approached. 



