1891.] ORGAN IN THE CROCODILIA. 149 



space between the premaxillo-maxillary sutures (s.m.), to be referred 

 to in full later on. This remarkable departure from the Crocodilian 

 type of structure was first described by Owen ^ ; Huxley redescribed 

 it seven years later " ; and both writers referred it to the one isolated 

 species named. Gray, with that mischievous originality for which he 

 •was so notorious, gave the character ^ as diagnostic of the genus 

 Jacare, and his error has been transcribed by Lydekker in the 

 ' Palasontologia Indica' *. it remained for Boulenger to rectify 

 matters ; and in having done so, to show ° that the feature remains 

 distinctive of the species (C niger) in which it was originally de- 

 scribed, and of none other. 



The leading fact that the vomers of Caiman niger are, at their 

 point of intercalation between the premaxillo-maxillary bones, inflated 

 and buUate (vo.'", iig. 2) was apparently known to Owen (loc. cit.) ; 

 and a detailed account of the general relationships of these bones 

 has been given by Huxley ^ Their remarkable characters, however, 

 have neither received that attention which they deserve, nor have 

 attempts been thus far made to decipher their meaning. It is 

 precisely this gap in our knowledge which, thanks to some specimens 

 generously placed at my disposal by Prof. Huxley, I would now 

 attempt to fill. 



The vomers of the short-snouted Crocodilia in ordinary {vo.', fig. 1) 

 usually commence to taper anteriorly at a point more or less verti- 

 cally disposed above the maxillo-palatine suture {s.mp.). There is 

 much variation individually and with age in respect to the exact 

 position of the point referred to ; but while it generally lies behind 

 the suture named, it may more rarely be situated in front of it (ex. 

 Alligator mississippiensis, fig. 4). From this point forwards, each 

 vomer rapidly tapers and disappears on the upper surface of the 

 palatine process of its corresponding maxilla {onsc.'), and wiih that it 

 may become early ankylosed (ex. Crocodilus niloticus). In Caiman 

 niger, however, the vomers {voJ , fig. 2) pass on to the middle 

 maxillary region (i. e. beyond that point at which these bones 

 ordinarily cease altogether in other Crocodilia) before they commence 

 to taper ; instead of dwindling away to a pointed extremity, they 

 descend, becoming bullate as they do so, and, thrusting them- 

 selves between the maxillary bones, terminate as aforesaid within 

 the palatal region. These expanded intercalary extremities of the 

 vomers {vo!" , fig. 2) may be appropriately termed their palatine lobes. 



The Crocodilia and Hatteria are exceptional among living Reptilia 

 in that their " pterygoid bones send forward median processes which 

 separate the palatines and reach the vomers " "^ ; an essentially similar 

 condition appears to be realized in some Chelonia by the backward 



^ Cat. Ost. Ser. E. Coll. of Surgeons, vol. i. p. 1G6 (1853). 



^ Loc. cit. p. 4. 



^ Brit. MuB. Cat. Shield Eept. ii. p. 25 (1872). 



^ Vol. X. (iii.) p. 210 (1885). 



= Loc. cit. p. 293. 



® Loc. cit. pp. 4-5. 



^ Huxley, Quart. Journ. Greol. Soc. vol. xrxi. p. 426 (1875). 



