192 PROP. W. K. PAEKEE ON THE STEUCTUEB AND 



upper margin as wings of the posterior sphenoidal region; these are the unossified 

 counterparts of the " sphenotics " of bony fishes, the roots of the " supraorbital bands." 



"A ligamentous band passes from this projection to the eye-ball" (Huxley, oj). cit.), 

 which is very small, and is attached by this band to the anteorbital {e.pa) ; this band is 

 a membranous " supraorbital." 



Halfway between the ascending process and the optic passage [a.]}, ii) the " sphen- 

 ethmoid " bone {sj).e) begins ; it is an ossification of the trabecula and its orbital crest, 

 and therefore answers both to the orbitosphenoid and lateral ethmoid, and also to the 

 primary half of the girdle-bone of those " Anura " which have an extension of bone 

 into the orbitosphenoidal region, as in Bactylethra. 



This ossification reaches in front of the ethmoidal region, and affects the hiad part of 

 the intertrabecula and cornu trabeculse {i.tr, c. tr) ; it meets its fellow below in the 

 adult (PI. XXXVIIL). 



We have here, in bone, the simplest rudiment of the lateral ethmoid and cribriform 

 flate of Man; for the olfactory nerves (i) are seen emerging obliquely from the 

 cranial cavity, and escaping beneath and to the inside of the aliethmoid {al.e), which 

 answers to the roof of the "upper turbinal" of Man. These wings are straight- 

 edged, look outwards and forwards, are not ossified to their end, and carry the rudi- 

 mentary nasal roof {no) or " aliseptal " cartilages ; these are ear-shaped, and cover only 

 part of the nasal capsule. 



Behind and below these wings another and rather smaller pair {tr) is seen ; these are 

 the flat hinges for the ethmo-palatine (ichthyic "palatine") cartilages {e.'pa); they 

 also are not ossified to their end. 



In front of the sphenethmoid the endocranium forms a trifoliate structure : the outer 

 " leaves " are the flattened, ear-shaped, outturned cornua trabeculse (c. tr) ; and the 

 median part, which is thick and oval in the middle, ends in a rounded and papilliform 

 " prenasal " projection {i.tr,]}.n) ; this median process is seldom seen in the Urodeles, but 

 occurs in Salamandra. 



All the three terminal processes are decurved ; both the upper and lower jaws are 

 bent downwards, accordiag to the primordial endocranial pattern. 



c. The Visceral Arches of Siren lacertina. 



Attached to the hinder and lower ethmoidal wings are a pair of pyriform cartilages 

 less than the nasal roofs, and attached by their broad ends; these are the ethmo- 

 palatines or true palatine elements {e.]}a). These are separated by the whole orbital 

 region from the piers of the mandibular arch [sp), which are very large cartilages, but 

 have no qnasi-symj)Iectic outgrowth (pterygoid cartilage). 



These latter, large, multilobate cartilages are complicated by the fusion with those of 

 the pier of the hyoid arch {e.hy) ; they are totally unossified (unique in this respect), and 

 retain the embryonic direction, which is forwards and outwards. The dorsal end of each 



