Tui: ilvoiD Bone in Mastodon A.mericanus. 



465 



described by Warren in 1852, in his work entitled " The Mastodon 

 Giganteus of North America," p. 13. The cranial extremities of the 

 bones show well defined articular surfaces, the depressions and eleva- 

 tions in which are homologous in the bones of the left and the right 

 hand sides. (See P^ig. 2.) A layer of fibro- 

 cartilage probably was interposed between the 

 styloids and the os tcinporis. 



The description of the styloid liones given 

 by ^^'arren, which applies well to the specimen 



before the writer, is as follows : p,j. 2 Articular sur. 



" The styloid processes are both perfect, face of right styloid proc- 

 measuring more than nine inches in length, ess of Mastodon Ameri- 

 They are attached at the base of the petrous por- ''""'•' '^^'■'■- ( ^''^'- •'^'^'^- ) 

 tion of the temporal bones. This process is rarely seen in ])lace ; but 

 in the head of a young elephant we find it connected with the tem- 

 poral bone by a ligament. The cranial extremity of this bone, pre- 

 senting the marks of the attachment of a fibro-cartilage, which inter- 

 vened between it and the os temporis, is more than an inch across its 

 longest diameter. From this end the bone tapers with some degree 

 of regularity to its cervical extremity, which is pointed. The bone is 

 cur\ed at its upper part; and one side of the curved portion is fluted 

 like the human clavicle, where the subclavian muscle lies under it. 

 The texture of the bone is c^uite dense; for which reason it has been 



preserved in a state of perfect 

 integrity, notwithstanding the 

 slenderness in its form." 



The Basi-hyal Bone (Figs. 

 3,4, 5). — The extreme length 

 of the bone, measured at the 

 symphyses with the thyro- 

 hyals, is 15.5 cm. The thick- 



ness at the middle is 2.q cm. 



Fig. 3. Inferior view of basi-hyal bone of 

 Mastodon Ameruantts Kerr. A, Anterior 

 margin ; B, posterior margin ; TH, TH, in- 

 ferior extremities of thyrohyals. ( \i nat. size. ) 



It is, roughly speaking, trian- 

 gular in section at the middle ; anteriorly longitudinally convex, 

 posteriorly longitudinally concave. A strongly defined, somewhat 

 recurved ridge is develoi)ed on the anterior surface, dividing it into a 

 superior and an inferior portion. The free surface of the upper mar- 

 gin between the two thyro-hyals measures 7.25 cm. in length. At 

 either end of the basi-hyal, at the points where it coossifies with the 



