THE MARSIPOBRANCHII. 135 
to them and unrepresented in the higher vertebrata, the 
question how far the abovenamed median ventral cartil- 
ages may be comparable to the basi-mandibulo-hyo-bran- 
chials of the latter, as Muller, Huxley, and Parker, have 
together sought to show, must remain in abeyance, until 
more is known of the development of these fishes. The 
safest course for the present lies in regarding them as 
peculiar to the Marsipobranchii, especially if Furbinger’s 
assertion* that a corresponding tract at the base of the 
tongue may be ligamentous in Myzine altho’ invariably 
chondrified in Bdellostoma shall prove correct. 
The greatest difficulty arises in dealing with those parts 
which in the Myxinide support the peri-oral folds, with 
their derivative tentacles. 'The most satisfactory descrip- 
tion of them is the classical one of Joh. Muller. Neither 
Furbinger nor Parker dealt with them in detail, and the 
latter author finally concluded (Phil. Trans. 1883, p. 404) 
that they were ‘‘ merely barbels,” refusing to admit them 
“perfect labial cartilages.” They are usually five in 
number on either side. One (/), borne upon the basi- 
ethmoidal rod may be dismissed as probably distinct from 
the rest. Of the four which remain’one (Jb. 1) supports 
the dorsal tentacle; a second (/d. 111) enters the lateral one ; 
a third (Jb. iv) les within a fleshy fold below the mouth ; 
while the fourth (Jb. 1) 1s T shaped, sending in a rod or 
process which abuts against the main cartilaginous sup- 
ports for the lateral head region.t In the Lamprey the 
sucking-mouth is mainly supported by the great annular 
SLOG NeUbs, Puro. 
+This ‘‘rod or process” may or may not be an independently distinct 
element, in individual specimens of both Mywine and Budellostoma (ef. figs. 2 
and 6). It is apparently that referred to by Fiirbinger (cf. supra) as 
fibrous in the firstnamed genus. In all examples which I have examined it 
is densely chendrified, altho’ in one of them it partook of the nature of the 
‘soft cartilage” of W. K. Parker. 
