Chap. VIII.] 



THE SKELETON. 



'55 



(1.) The Brain-Case. The three typical segments are not 

 represented in bone. In the hinder segment there is no basi- 

 occipital, and the supra-occipital is not represented. On the 

 other hand, the ex-occipitals (e. o.) are large and well developed, 

 and may comprise also the epiotic and opisthotic elements. There 



p. mi, p. mi. 



E. 



FIG. 50. SKULL OF FROG. 



A. Chondrocraniuni, with invading bone, from above. B. Skull from below. 



C. Skull from above. D. Hyoid. E. Lower jaw. 



a. c. Anterior cornu of hyoid. a. /. Anterior fontanelle. a. n. p. Ali-nasal 

 process, a.o.p. Antorbital process, an. sp. Angulo-splenial. aw. c. Auditory 

 capsule. &. h. Basi-hyal. d. Dentary. e. n. External nares. e. o. Ex-occi- 

 pital. /. o. Fenestra ovalis. i. n. Internal nares. w. irik. Mento-meckelian 

 (probably from lower labial cartilage), tnx. Maxilla, n a. Nasal, p. ft. 

 Pterygoid bone. p. c. Posterior cornu of hyoid. p. f. Posterior fontanelle. 

 p. fr. Parieto-frontal. p. mx. Pre-maxilla. p. n. p. Pre-nasal process. 

 pa. sp. Para-sphenoid, pi. Palatine, pr. o. Prootic. pt. Pterygoid. pt. c. 

 Pterygoid cartilage, q.j. Quadrato-jugal. r. p. Rhinal process, s. e. Sphen- 

 ethmoid. sq. Squamosal. sus. Suspensorium. vo. Vomer. 



are two occipital condyles. In the parietal segment there is no 

 basi-sphenoid and no ali-sphenoid. The parietals are, however, 

 fully developed, and in comparatively young frogs completely 

 fuse with the frontals to form the parieto-frontals (p. fr.). In 



