SKELETON OF CYCLOSTOMES. 



65 



are three in the Sea-lamprey, of which the middle one is 

 joined to the palate by an intermediate smaller one ; the fore- 



Fig. 30 . — Upper (A) and side (B) views, and vertical section (C) of the skull of 



Petromyson marinus. 

 a, Notochord ; 6, Basis cranii ; c, Inferior, and d, Lateral process of basis ; e, 

 Auditory capsule ; /, Subocular arch ; g, Stylohyal process ; h, Olfactory 

 capsule ; i, Ethmo-vomerhie plate ; Ic, Palato-pterygoid portion of subocular 

 arch ; l-n, Accessory labial or rostral cartilages ; •with o, appendage ; p, 

 lingual cartilage ; q, neural arches ; r, Branchial skeleton ; s, Blind termina. 

 tion of the nasal duct between the notoohord and oesophagus. 



most is ring-lilce, tooth-bearing, emitting on each side a styli- 

 form process. The lingual cartilage is large in all Cyclostomes. 



