DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 233 



Fourth Ftimlly. " Piiryniscid.e." 

 Toes webbed ; sacrum broad ; no ])arotoids ; ear generally very imperfect. 



Genus Phrijniscus. 

 68. Phryniscus cruciger. — Adult male; 1^ inch long. Interior of Brazils. 



The small skull of this species (Plate 41, figs. 1-5) has its breadth one-thirtieth 

 greater than its length ; its outline, up to the hinges for the lower jaws, is nearly 

 triangular, but the extreme end of each hinge (q-c.) is opposite the centre of the Eusta- 

 chian opening (e».), so that much of the skull — all the hind skull — lies behind the 

 facial margin, as in newly metamorphosed Anmu of a high type. 



The whole skull has the appearance of an abortively developed Bufonine structure, 

 with an abnormal amount of ossification ; it is like a badly developed skull of such 

 a form as £ufo ornatus, or of the half-grown Otiloplius (Plate 37) ; moreover, it is 

 asymmetrical to a degree very seldom seen in the group ; more so than that of Siredon 

 among the Urodeles. The foramen magnum {f.m.) is large and obliquely superior ; 

 the occipital condyles (oc.c.) are large, sub-pedunculate, and directly posterior. Out- 

 side them, the epiotic and tegminal projections (p..s.c., t.ti/.) are a little and a little 

 further forwards, and yet, on the whole, the lai'ge hind skull is a broad transverse 

 tract, the "canals" standing out of it well, and the wide tegmina, bounded by the 

 squamosals (sq.), enlarging gently, forwards. Two-tliirds of the tract beyond the 

 horizontal canal (h.s.c), on each side, is cartilaginous ; from the hind margin of the 

 optic fenestra (II.) to a distance twice the extent of that space there is cartilage ; and 

 the snout (j^.«.) in front of the ni\sals (n.) is also soft. 



The rest of the cranium proper is bony, and in some parts these extensive ossifica- 

 tions are anchylosed to the investing bones. 



Measured along the axis, the three regions are sub-equal ; they are all very broad ; 

 and, taking in the face, the outline becomes just less than a right angle; for' the 

 I)roper cranial margins run inwards rapidly from behind, foi'wards. The temporal 

 region is of great breadth; the orbital edge is concave; the main fontanelle (fig. 1), 

 contrary to wont, is widest across — like a Tortoise's heart ; near it, behind, the other 

 two spaces are large and circular ; the laiger space is not quite covered. 



The girdle-bone (e<^.) leaves only a small orbito-sphenoidal tract (o.s.), behind, and in 

 front runs to the fore edge of the nasals (n.) above (fig. 1), and to the premaxillaries 

 below (fig. 2, 2^oc.) ; it takes in the " wings," above, and the palatine flap, also, below ; 

 moreover the palatines are anchylosed with it (figs. 1, 2, ep.a., pa.), the bony "alee" 

 touching the pterygoids {pg-) ; the vomers (i'.), also, are confluent with the large 

 girdle -bone. 



The nasal roof and septum (figs. 1-3) are formed into an over-hanging decurved beak, 

 with a sinuous outline ; this pre-nasal {p.n.) is a mere thickening of the middle part, in 

 front, as in the embryos of many Vertebrata at an early stage ; this arrested (or genc- 



MDCCCLX.XXl. -2 II 



