180 PROF. W. K. PAEKEE ON THE STEUCTUEE AND 



On the Skull of the adult Menopome. 



This is a very flat skull, with the general outline semielliptical ; the suspensoria 

 form more than a right angle with the axis of the skull, and therefore are somewhat 

 bent backwards. The narrowest part of the occipital ring and the condyles are alone 

 behind the larger condyles of the suspensorium. 



The maxillary margins reach more than halfway to those condyles ; for these bones 

 are well develojied for a Urodele. 



There are two tracts of teeth in both the skull and mandibles ; the whole fore palate 

 and maxillary region is nearly semicircular. 



There are very large pterj'goids ; and these are far removed from their root, viz. the 

 palatines; altogether this skull has undergone much more metamorphosis than the 

 Eel-like types, viz. Proteus, Menohranchus, and resembles that of the young of an 

 average " Caducibranch " when losing its gills. 



The inferior arches are very large, and, instead of undergoing the metamorphic 

 changes and loss of substance as in the higher forms, become strongly ossified, without 

 any relative change of form or size ; so that this type really belongs to the " Proteidea." 



A. The Investing Bones of the Skull of the Menopome. 



lloofing-plates of bone extend from the foramen magnum to the snout (PI. XXXVIII. 

 fig. 1) ; and flooring-bones extend from the edge of that passage up to the marginal bony 

 arc (PI. XXXVIII. fig. 2). 



The hindermost of the upper series, the parietals {p), form, on the whole, an oblong 

 tract, reaching from the foramen magnum to the ethmoidal region ; they widen out 

 over the auditory capsules, and are deficient on their inner edge in front, where the 

 frontals (_/') wedge themselves in. 



Their dilated and raised temporal process has the two forks of the squamosal {sq.) 

 locking into it obliquely ; their inner part, alongside the sagittal suture, is somewhat 

 roof-shaped, but scarcely amounts to a ridge ; together they are only three fifths the 

 width of the skull-floor. The obtusely angular and notched hind part of these bones 

 only partially covers the widest part of the occipital cincture. 



The frontals (_/") are only half the size of the parietals ; together they cover a 

 Y-shaped tract ; for these bones are narrow toothed wedges behind, whilst in front 

 they widen somewhat, and are divaricated to let in the nasals («), much more than the 

 parietals did to take them in. 



Their outturned fore end is overlapped by the round-edged ascending plate of the 

 maxillaries [nur) ; and this part almost reaches the outer nostril {e.n). Here the nasal 

 roof is exposed behind the passage as a pyriform tract of cartilage, whose point ends 

 between the frontal and nasal. 



The nasals [a) have a toothed suture between them, which continues the open 

 sutural line along the low ridge of the skull ; they also are wedges, broad in front and 



