88 MR. w. K. PARKER ON THE STRUCTURE AND 



The palato-suspensorial arches and their relation to the nasal region are like those 

 of the fourth of my stages of Pseudis (see Plate 12). The " ethmo-palatine" (e.pa.) is 

 a thick traiisvei'se bar, whose flattened upper end articulates with the ethmoidal wall. 

 The " pre-palatine " (pr.jKi.) is split into two laminae, the outer one is rounded, and the 

 inner and upper lobe is sharp ; the outer runs into a second spike, turning inwards on 

 the transverse bar (fig. 2). The "post-palatine" (pi.^xt.) now forms a crescentic crest 

 on the top of the far-extended pterygoid caiiilage (pf/.), where it turns inwards, in 

 front. 



The former was ft'ee behind ; and its new and fixed position, as compared with its 

 original condition, is well seen by comparing my third and fourth stages of Pseudis 

 (Plates 11, 12). 



The rest of the arch keeps its even size as a rather wide band, until it forks ; tlie 

 short inner fork is the pedicle {pd-), the longer outer fork is the quadrate and its 

 hinge [q., q.c), which reaches to a line crossing the middle of the stapes (st.). The 

 palatine and pterygoid bones {pa., pg.) are normal : the former looks like the bone of 

 an old individual ; the latter is thin and arrested. 



The Eustachian openings («/.) ai'e large and turned obliquely outwards and for- 

 wards ; the stapes (figs. 5, 6, st) is an elegant oval, and has wedged inside its front 

 margin a nnich smaller oval cartilage quite distinct — the interstapedial hind part 

 of the columella. The main part of the columella {co.) is not developed into regions; 

 it is long, sinuous, and finger-shaped, with a crest near the stapes : but for the separate 

 interstapedial, this columella would have corresponded with that of Pseudis at its 

 fourth stage (Plate 12, fig. 6). The narrow "annulus" {ci.ty.) is arrested ; it is a knee- 

 shaped strap of cartilage bent forwards. 



The mandible and hyo-branchial plate (figs. 3, 4) correspond with those of a very 

 young Frog; tlie mento-Meckelian is not finished, and the cerato-hyal (<"./(//.) runs 

 short of the ear-capside; there is no hypo-hyal lobe, and only the hinder part of lateral 

 lobes. 



Nearly all the investing bones have the same arrested character ; the j^arasphenoid 

 (fig. 2, p«.s.) is, however, very large ; the vomers (v.) are small, angulated crescents, 

 without teeth. 



The fronto-parietals fail to cover more than half of the great fontanelle ; this cor- 

 responds to what has been found in other species of this genus.* 



The deflection from the norma seen in this small skull is very largely due to arrest, 

 on account of the small size of the species, and perhaps also to a somewhat immature 

 state. These deficiencies, as compared with the skull of an adult of the common kind 

 are : — 



* Professor E. D. CorE — "Eleventh Contribution to Herpotology of Tropical America," Amer. Phil. 

 Soc, June 20fch, 1879, p. 264 — says that Leiuperun (a s^iiouym of Gomphobates) lias an open fontanelle. 



