21Q MR. W. K. PARKKK ON THK STRUCTURE AND 



lust ; and this part shows, on its under suriace, threads of new membrane -bone — 

 the parasphenoid (fig. 10, jja.s.) is appearing. 



The notches for the inner nostrils {i.n.) narrow the skull very much ; and in this, 

 as in the last, the quadrate cartilage (q.) shows a slight enlargement, which is 

 attached by a membranous ligament to the point of the cornu (ctr.) in front of the 

 notch ; the projection on the quadrate part of the suspensoiium is the rudiment of the 

 pre-palatine spike. 



The rudimentary ethmoidal wing (al.e.) is a mere angular projection at present, 

 and is much smaller than in the last kind ; the elevation on this band is the rudiment 

 of the post-palatine bar {i^t.pa.). The mandibles [mk.) are like those of the last, l)ut 

 not so massive ; the same may be said of the lower labials (A/.). 



But the upper labials {u.l".u.V'.) differ from those of the last Tadpole ; they are 

 formed as two on each side, at the first, and do not become two by segmentation. The 

 two inner pairs, if melted together, as in the larva of Rana pij^^iens, would answer 

 to the anterior dorsal cartilage of the Lamprey ; the styliform outer cartilages answer 

 exactly to the external pieces in that Fish. 



Here the orbitar process {pr.p.) is still further from the ethmoid than in the last, 

 and yet it possibly may unite with it afterwards. 



The hyoid bar (cJuj.) is narrower in its shaft, and dilates into tw^o still more 

 projecting angles distally ; the hinder of these is the stylo-hyal rudiment, the large 

 cells at the lower end form part of the basi-hyal tract. Part of the first "extra- 

 branchial" {ex.hr^.) is shown in relation. In neither of these instances is there any 

 rudiment as yet of an " epi-hyal " element. 



A comparison of these crania with those of the larval Frogs, already described, will 

 show to what degree the skull may differ in its initial {Petvomi/zine) stages. I now 

 come to the description of the newly metamorphosed skull of this Toad, to be used as a 

 standard of comparison in describing the skidls of the small, arrested glandless Toads 

 (" Phryniscida)," " EngystomidEe"). These small kinds will l)e found to have skulls 

 arrested at various points that correspond with what is seen at the diflerent periods of 

 life in the higher and more developed kinds. They also show very instructive 

 instances of a sort of relapse into old ichthi/ic conditions; they resume characters that 

 have been suppressed in the more normal and better developed Anura. 



59 (continued). — (B) Skull o^Biifo lentiginosns, — Recently metamorphosed; f inch long. 



In the skull of the young Toad of the first summer (Plate 39, figs. 7, 8, 9) tlie length 

 and breadth are equal, and the quacU-ate condyles {q.c) reach, as yet, no further back 

 than the Eustachian openings (eu.). Up to that part the form of the skull is a very 

 neat semi-ellipse, and behind tlie lound edges of the tegmen tympani (right and left) 

 {t.tij.), the cpiotic emmences { p.a.c.), and the occipital condyles (oc'.c), all may be said 



