132 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
orbital) and pterygo-quadrate cartilages,* is, as Huxley 
first intimated,t more embryonic than that of the Lam- 
prey. There is thus good reason for concluding that 
the higher Amphibia have reached the supposed Marsipo- 
branch stage in the evolution of the skull, by an inde- 
pendent line of modification. The argument deduced 
from the study of the external gills and sucking mouth 
(ante, p. 180) applies here, and, in doing so, still further 
diminishes the force of that in favour of a Marsipobranch 
ancestry for the Anura. | 
VI. All recent enquiry into the morphology of the 
cranio-facial apparatus of the Marsipobranchs finds its 
focus in Huxley’s monograph already cited, in which the 
presence of true jaws was first demonstrated and the 
complex apparatus of the Petromyzontide was brought 
into harmony with that of the higher enathostomata. 
Huxley alluded to the Myxinoids but incidentally (op. cit. 
p. 428); Furbingerf and Parker§$ have however dealt 
more fully with their head skeleton from the modern 
standpoint. Neither author’s description at all bears out 
Huxley’s stray remark that ‘‘ there is even less difficulty 
in reducing the skull to the ordinary vertebrate type”’ 
* The fusion of these to form a complete sub-ocular arch, like that of the 
Batrachia, occurs only in Ranodon (Wiedersheim, Morph. Jhb., Bd. III, p. 
425). The recent discovery by Riese (Spengel’s Zoolog. Jahrb., Bd. V, 
[Morph. Abth.,] p. 114) of a quadrato-jugal bone in the Eastern Tylotriton 
verrucosus, raises the question whether the great reduction of the pterygo- 
quadrate cartilage of the majority of Urodeles may not be associated with that 
marked tendency towards suppression of the maxillo-jugal elements, so conspic- 
uous in them ?—a feature in which, as in the non realization of a type possessed 
of pentadactyle fore and hind limbs, the living Urodela show themselves to 
be more aberrant than the Anura. 
t Proce. Zool. Soc., Lond., 1874, p. 193. 
tJenaische Zeitschr. Bd. IX, pp. 1—127, 1875. 
§ Phil. Trans., 1883, pp. 873—453. 
