4 8 



MYXINOIDEA 



The anterior region of the subintestinal vein seems to persist to 



nap. 



ct. 



Via. 30. 



Median longitudinal section of the anterior region of Rdellostoma Forsterii, M. (Modified 

 from Parker.) b.c, buccal cavity ; b.pl, basal plate of ' tongue ' ; br, brain ; c.t, cartilage ring of 

 nasal tube ; et, median horny tooth ; f.t, fatty tissue ; h.p, hypophysial plate ; h.s, hypophysial 

 sac opening behind into pharynx ; m, mouth ; nac, nasal tube ; nap, median nostril ; n.ca, nasal 

 capsule, with cavity divided by median septum ; nt,, notochord ; oe, pharynx ; p.p, parachordal 

 plate ; pt, rasping organ with horny teeth ; sre, subnasal cartilage ; t, cartilage of ' tongue ' ; 

 c, velum. The cartilages are dotted. 



va 



CO. 



FIG. 31. 



Diagram of the gills and their afferent blood system in A, Bilellostoma (Homen stout i); B, 

 Paramyxine ; and C, Myxiiie (after Dean). Ventral view, c.o, common opening of six gill-sacs 

 and oesophageal duct ; b.s, gill-sac ; d, oesophageal duct ; h, heart ; o, external opening of 

 gill-sac ; ph, pharynx ; t, outline of rasping ' tongue ' ; t.e, tube leading to exterior ; v.a, 

 ventral aorta. 



a considerable extent in the adult as a vessel carrying blood from 

 the intestine through the liver direct to the sinus venosus (Fig. 32). 



