XIII 



PHYLUM CHORDATA 



119 



The tongue is supported by a long unpaired lingual cartilage 

 (Fig. 750, Ig. c.), which probably answers to the basi-hyal or 





flTl.C 



CL.d.C 



B 



- TIC/I 



p.lat.c 



crv.c 



FK.. 751. Petromyzon marinus. Dorsal (A), ventral (B), and sectional (C), views of skull. 

 The cartilaginous parts are dotted, a. </. <\ anterior dorsal cartilage ; an. c. anmilar cartilage ; 

 au. <. auditory capsule; />. <v. f. basi-cranial fontanelle ; 1>. pi. basal plate; o. t\ comual 

 cartilage ; (/. ;-. cranial roof ; tin. np. nasal aperture ; ndi. notochord ; JY<-. 1, olfactory nerve ; 

 NI-. -2, ':, and S, foramina for the optic, trigeminal, and auditory nerves ; J\v. 5', fifth nerve ; 

 olf. <. olfactory capsule ; p. </. c. posterior dorsal cartilage ; p. Int. e. posterior lateral cartilage : 

 xii. oc. a. sub-ocular arch ; *t. p. styloid process. (After W. K. Parker.) 



median ventral element of the hyoid arch of other Craniata (see 

 p. 71) : it is tipped in front by a small median and a pair of still 

 smaller lateral cartilages. Below it is a slender T-shaped i 



