184 PEOF. W. K. PAEKER ON THE STEUCTUEE AND 



crescentic space, we see a broad elbowed tract of cartilage ; this is the ethmo-palatine 

 {e.pa) ; it arises from the trabecula, where it has grown into the ethmoidal wing ; 

 with this wing the palatine cartilage is confluent. In Siren (PI. XXXIX. figs. 3, 4) the 

 homologous cartilage is quite separate, both from the nasal roof and from the ethmoid. 

 The suspensorium is a very massive and complex structure ; it is partly ossified, and 

 to some extent confluent with the next arch, and also at three points with the endo- 

 cranium. The pedicle (fig. l,pd) passes into the basis cranii above the angle formed by 

 the divergence of the pterygoid and parasphenoid (fig. 2,pg,pa.s) ; the ascending process 

 (fig. 1, a.p) passes into the " alisphenoidal " wall in front of the foramen ovale (v) ; out- 

 side that foramen, at a distance equal to its heiglit, the otic process {ot.pi) has become 

 confluent with the auditory capsule in front of the middle of the squamosal {sq). The 

 body of the suspensorium is narrow at that part, and then expands greatly below ; its 

 direction is mainly outwards, but also a little backwards and downwards ; it is thickened 

 behind ; and this thick edge ends in a free process above. 



The oblique subreniform condyle [q. c) is extremely large ; its broad end is behind and 

 a little within ; above this condyle the fore part of the lower half of the bar is well 

 ossified as a quadrate bone. 



There was a large qiiasisympilectic cartilage growing from the fore margin of 

 the suspensorium, viz. the pterygoid cartilage ; this has been largely ossified by the 

 pterygoid bone, and only a tongue-shaped piece is left in front ; it looks outwards 

 and lies in a groove in the bone ; this is now a separated primordial " epipterygoid " 

 {e.pg). 



The articular part of the lower jaw (PI. XXXVIII. fig. 4, ar, ar. c) is to some 

 extent solid bone due to the grafting of the superficial " articulare " on the cartilage, 

 which, however, persists inside the ramus. The condyle is oblique, sinuous, and sub- 

 reniform. 



The articulare is only visible, below and within, up to the foramen for the nerves and 

 nutrient vessels ; it is wedged in between the large dentary and almost equally large 

 splenial {d, sjjI). 



The hyoid arch is composed, altogether, of six pairs of pieces and an odd one ; there 

 is on each side a pharyngohyal, an epihyal, a ceratohyal, and three hypohyals, these 

 latter, right and left, being united by a small basihyal (PI. XXXVIII. figs. I, 2, and 

 PI. XXXIX. figs. 4, 5). 



The pharyngohyal element {p-hij) is for tlie first time in the vertebrate series used 

 as a " mediostapedial ;" it is shaped like a small bell-flower, being dilated into the 

 campanulate form, distally ; this broad end is set against the hind margin of the 

 squamosal (sq). Behind and above its narrow rounded end (apex) is enclosed in a 

 calyx of bone derived from the discoidal ossified stapes (st) ; the cup for the medio- 

 stapedial cartilage is an oblique outgrowth from the fore part of the disk. 



Between the mediostapedial and the small fork of the squamosal (PI. XXXIX. 



