BRANCHIAL SKELETON. 103 



53), i.e. the palatine process of the trabecular region is directed backwards 

 and not merely outwards as in lampreys (Fig. 50). Further the labial 

 cartilages of the lamprey, viz. the anterior dorsal, the anterior laterals and 

 the annular are not present in Myxinoids. On the other hand the oral 

 barbules of the Myxinoids contain a cartilaginous axis and the lingual cartil- 

 age is enormously developed (Fig. 53), and connected with the styloid 

 process (supposed hyoid arch). 



In the Petromyzontidae there is a branchial basketwork of 

 cartilage placed superficially, near the skin and supporting the 

 outer parts of the branchial passages. It consists (Fig. 50) of 

 eight irregularly curved bars of cartilage placed between the 

 successive gill sacs.* They are connected dorsally by a longi- 

 tudinal band of cartilage, which lies along the notochord sheath 

 and is con inuous with the hind end of the skull, and by three 

 other longitudinal bands, of which two are lateral, one being 

 above and one below the branchial apertures, and one is ventral 

 and partly fused with its fellow. The branchial basket is con- 

 tinuous posteriorly with a cartilaginous cup which supports the 

 wall of the pericardium (Fig. 50, 22). The first branchial aper- 

 ture is behind the first bar, and the seventh or posterior in front 

 of the last bar. 



The branchial basketwork is supposed to be developed in the somato- 

 pleure and not to be homologous with the branchial arches of other fishes 

 which lie in the gutwall. The only representative of these structures in 

 Myxinoids (in addition to the supposed traces of mandibular and hyoid 

 arches) is the structure described above as the first branchial arch (Fig. 53, 



2J:). 



The alimentary canal. The mouth, or buccal fumiel (Fig. 

 54), is suctorial and armed with horny epidermic teeth ; in the 

 lamprey it is surrounded by a lip carrying short papillae, in 

 Myxinidae by eight barbules (Fig. 61). On the ventral side of 

 the mouth is the tongue, which, moving backwards and forw^ards 

 like a piston, enables the animal to attach itself by its mouth as 

 by a sucker. The tongue carries teeth (two rows in the myxinoids 

 on the supralingual cartilages), which enable it to inflict con- 

 siderable wounds upon its prey. The buccal funnel leads into a 

 tube, which is supposed to be stomodeal, and may be called the 

 buccal cavity. This is continued behind into the oesophagus, 



* There appears to be some variation in the details of the arrangement 

 of the branchial basketwork in the different species (cf. W. K. Parker's 

 account with Schneider's figure). 



