168 PEOF. W. K. PAEKEE ON THE MOEPHOLOGT 



modification of the " epihyal " element as one sees in most Batrachia. The hasal ele- 

 ment is deficient in the first two arches, but the second arch is attached to the fore end 

 of the first basibranched piece ; there are only a first and a second ; and the hyoid and 

 two first branchial arches are attached to the foremost piece (fig. 3, h.hy, c.br 1 , c.br 2 , 

 b.br 1 , b.br 2 ). 



The free mandible (mk) is a single rod, right and left; it undergoes no subterminal 

 segmentation. This pair of bars is united together by membrane, so as to form a half- 

 bent bow. The distal end of each is slender and terete, but further up it gradually 

 becomes very solid, suddenly narrowing again, to form a rounded angle. Near the angle 

 above there is a transverse condyloid region, not very distinct from the rest of the car- 

 tilage. These bars alone have bony films upon them ; they will be described with the 

 other bony deposits. The length of the mandible (ink) and its place of articulation with 

 the suspensorium correspond with what we find in the Frog when the gills are wasting. 



In the hyoid bar the slender part is above, and the thickening, which is sudden, is 

 retained, with but little diminution, to the rounded extremity. This bar is Hatter than 

 the mandible, and has its distal fourth segmented off to form a hypohyal (fig. 3, c.hy, h.hy). 



Its size, thickness, and position with relation to the suspensorium correspond with 

 the stage of the Frog just mentioned. 



Each bar passes within, and is attached by ligament to, the mandible ; the distal end 

 of each hypohyal is loosely tied to the fore end of the first basibranchial (h.hy, b.br 1 ). 



Of the next four arches, the branchials, only the two first have a distal or cerato- 

 branchial element; and the last epibranchial piece (e.br A ) does not carry gills. The 

 first and last have one, and the second and third two rows of denticles forming the gill- 

 colander ; the four epibranchials lessen from before backwards elegantly. They are all 

 falciform, but rather thick. 



The first basibranchial (fig. 3, b.br 1 ) is evidently the keystone of the two foremost 

 arches, their ceratobranchials being articulated with it ; it is high, but thickish also, 

 and its greater height is in front of the first branchial. The second basal piece (b.br 2 ) 

 is a flattened spatula, whose narrow attached end is articulated to the lower edge of the 

 first basal segment ; it ends behind in a broad blade, whose margin is straight. 



The osseous centres are already numerous ; the largest of these is the parasphenoid, 

 which forms a thin floor of lath-like bone to the base of the chondrocranium from end 

 to end, or nearly. The apex of the notochord is ensheathed by an imperfect " cephalo- 

 style;" but this is now wasting, and is not distinct from the parasphenoid: in some 

 Caducibranchs (e. g. Seironota) this centre ensheaths the fore half of the notochord and 

 is autogenous. 



Above, the frontals and parietals are forming the roof ; these will be described in the 

 next stage ; the squamosals (sq) are applied as splints to the suspensoria. 



Distinct premaxillaries, dentaries, splenials, and articulars (px, d, sp, ar) are now well 

 seen ; the maxillaries (mx) are later in their appearance than these. 



The fore part of the palate is beset with teeth, like the pharyngeal teeth of Osseous 

 Fishes ; these are arranged in an arc on each side, whose concavity is inwards. The 

 fore part of each tract is broad, and in this part the teeth are cemented to a thin bony 



