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 



a.d.c 



nci.a 



n a. cip 

 olfc Nus 



p.lal.c 



crv.c 



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

 The cartilaginous parts are dotted, a. <l. c. anterior dorsal cartilage ; an. c. annular cartilage ; 

 ni>.. <: auditory capsule; >>. <-,-. f. basi-cranial fontanelle ; /;. pi. basal plate; en. c. cornual 

 cartilage ; o-. r. cranial roof ; na. ap. nasal aperture ', ncli. notochord ; Nr. 1, olfactory nerve ; 

 >, and 8, foramina for the optic, trigeminal, and aviditory nerves; Nr. 6', fifth nerve ; 

 off. c.'olfactory capsule ; p. </. c. posterior dorsal cartilage ; p. Int. c. posterior lateral cartilage ; 

 s6. oc. a. sub-ocular arch ; x/. 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 median 



