236 MR. W. K. PAEKER ON THE STRUCTURE AND 



69. Phrynisctis varivs. — Adult female ; 1 1 inch long. Costa Rica. 



The last species had the average relation of length to greatest breadth ; in this we 

 have, suddenly, one of the longest skulls in the group, the breadth being httle more 

 than three-quarters of the length ; the general outline is that of a parabola (Plate 41, 

 figs. 6-9). In some things the asymmetry is like that of the last kind, in others 

 the largest bone of a pair is on the opposite side. The ossification is more intense and 

 Salamandrian than in P. cruciger. The skull is still more depressed, and the deve- 

 lopment of some parts has suffered severer arrests. The fitting on of the head to the 

 spine is different, in that there was an almost directly posterior aspect of the occipital 

 condyles ; here (figs. 6-8, oc.c.) they are iMstero-iiiferior ; the foramen magnum {f.m.) is 

 still more oblique (superior in aspect) than in the last kind. Recently metamorphosed 

 young of normal Anura show nearly as great an extension of the parotic region 

 as this species ; for here the horizontal canal rims into the substance of the thick 

 unossified "tegmen" {t.ty.). That selvedge, a band above the huge optic fenestra 

 (II.), the lim of the duck-hilled snout, and the edge of the fenestra ovalis, are 

 unossified ; very little else of the cranium proper remains soft. Measured along the 

 axis, there is but little difference in the relative extent of the fore, middle, and hind 

 skuU ; the fore skull is somewhat longer than the rest, on account of the projection 

 of the snout. 



The semicircular canals project well from the bony hind skull ; the supraoccipital 

 region is short, the two oval and the large heart-shaped fontanelles {fo.,fo'.) are very 

 large; there is just an overlapjiing margin as a rudiment of the tegmen cranii running 

 along the sides, and enclosing the fontanelles. The mid skull is wide, making it look 

 short ; the teniporo-postorbital region is very wide. The mid skull bulges m the 

 middle (fig. 8), but shrinks in front ; the floor of the nasal region is like a highly 

 arched " haixl palate " in a human skull. The optic fenestree (II.) occupy nearly a 

 third of the orbital tract, and are almost as large as their counterparts for the setting 

 in of the auditory capsules ; the " serial homology " of these spaces can be well seen 

 in such a skuU as this. The girdle-bone extends from this space to nearly the verge 

 of the snout, and thus occupies three cranial regions, besides taking in the ethmo- 

 palatines (e.jja.), and uniting with the i^alatine ectostosis (j^d-)- The pro-rhinals 

 (Plate 40, fig. 10, p.rh.) are small, and the fore palate is narrower than in the last. 

 There is a narrow tract of cartilage on the edge of the upper sm'face of the pterygoid 

 (fig. 6, pg.), and the facet of the pedicle {pd.) and most of the quadrate {q.) are unossified. 

 The condyles {q-C.) are reniform, long, and veiy oblique, the left more than the rigid. 



The mandibles (fig. 9) show a long condyle also, and very large mento-Meckelians 

 {m.mk.) ; the dentary [d.) is very long, and the articulare {ar.) a mere trough for the 

 cartilage {ml\). This is neither annulus tympanicus, nor columella ; the stapes (figs, 7 

 and 8, st.) is large, oval, and umbonate. 



The stylo-hyul (figs. 7-9, st.h.) is adherent ; it is a narrow band, very slightly 



