222 



THE FROG— THE PLATANA 



Atlas 



-Transverse process- 



Cartilaginous rib-- 



.Transverse process 

 of 9th vertebra- - 



— Urostyle 



---Ilium 



■Ischium 



Urostyle 



Ilium- 



Ischium 



Fig, 



A ' B 



79.— A. The Vertebral Column and Pelvic Girdle of Rami ; and B. of Xenojms. 



4. Remove and examine the 8th vertebra, and note that the centrum is 

 amphieoelous.^ Make a draAving of a section showing the centrum. 



[The centrum is opisthoccelous in the Platana.] 



5. Remove and examine the 9th vertebra or sacrum, and note that the 

 centrum is sUghtly convex on its anterior surface. The urostyle articulates 

 with the two convex facets on the posterior surface of the 9th vertebra. It is 

 a rod-like bone gradually tapering to a point. 



[In the Platana the urostyle is fused to the posterior surface of the 9th vertebra, 

 and the transverse processes are long, flat, and wing-like.] 



Siosth Day 



Skeletal System (continued). 



C. The Skull. 



1. Remove the skin and other tissues from the top of the skull and ob- 

 serve the large fronto-parietals, sphenethmoid, nasals, premaxillse, maxillae, 



^ Amphicoelous means concave at both ends. 



