118 THE ANATOMY OF HYLA C.F.RULEA WHITE. 



region. The foramen magnum is slight)}^ compressed 

 dorso-ventrall}^ and it is completely surrounded by bone. 

 On the anterior surface of each otic wing is a horizontal 

 groove, and in the central portion is situated the auditory 

 recess leading to the auditory foramen. An extension of 

 the wall of the recess prev^ents it from being viewed 

 anteriorly. The hinder border of the optic foramen is 

 formed by the anterior margin of the pro-otic, which is 

 perforated more posteriorly by two small elongated foramina. 

 The maxillo-mandibular branch of the trigeminal issues 

 by the larger and more dorsal (fig. II, V,.) and the 

 ophthalmic of the same nerve b}^ the smaller (fig. II, V^)- 



The anterior fontanelle (fig. I, /) is partially roofed 

 over posteriorly by the fronto-parietals (fig. I, f.p.), but the 

 anterior portion is uncovered. The sphenethmoid {sjih.eth) 

 is extensive, strongly compressed dorso-ventrally and 

 roughly pentagonal in shape. Postero-ventrally the edge 

 is entire, but postero-dorsally it is deepl}^ notched for the 

 anterior margin of the fontanelle (fig. I). The postero- 

 lateral borders are concave, each with a prominence along 

 its length, which marks the position of the anterior 

 extremity of the overlapping fronto-parietal (fig. II, X). 



The antero-lateral borders approximate forming an 

 angle, which may be seen from the dorsal surface lying 

 between the nasals. The sphenethmoidal septum is well 

 developed, and on the floor of each olfactor}?^ recess is a 

 strong ridge running to the olfactory foramen. The nasals 

 (fig. 1, na.) overlap the antero-lateral borders of the 

 sphenethmoid, and in shape each is semilunar with the 

 concavitj^ anterior and smooth, but the convexity is 

 irregular. The ventral cornu is pointed and placed at an 

 angle to the major portion of the bone ; it comes into 

 relation with the inner side of the nasal process of the 

 maxilla (fig. I, na.ji). The greater portion of the median 

 ramus of the parasphenoid (fig. II, m.r.pa) is applied to 

 the ventral surface of the sphenethmoid. Its edges at first 

 slightly diverge, then converge almost to a point. On the 

 posterior border of the transverse limb in the mid line, is 

 an angular process (fig II, p). The arms of the transverse 

 ramus (fig. II, tr.r.pa.) extend outwards to near the auditory 

 recesses. The anterior extremities of the fronto-parietals 



