134 REPTILIA. 



Tailed Batrachia, e. g., Siren, only a single pair of ossicles is found 

 provided with teeth, and which admit therefore of being taken 

 either for palatal or vomerine bones. The superior maxillaries are 

 usually of very large size, being rarely, as in the Siren, in a minute 

 or rudimentary condition. The inter maxillaries are also consider- 

 ably developed. The inferior maxilla generally consists of an 

 anterior piece supporting teeth, and a posterior articular portion of 

 nearly equal length. A small ossicle is occasionally placed upon 

 its articulating surface, but is generally anchylosed thereto. A 

 fourth piece is seldom found in the middle of the lower jaw, as is 

 the case in the rest of the Amphibia. 



The Squamigerous Reptiles are characterized by the greater 

 extent to which ossification is carried in the several bones com- 

 posing their skull, many parts that in the naked Amphibia were 

 only membranous having become in them converted into bone. The 

 individual bones of the cranium are here also multiplied by division, 

 as is especially exemplified in those that enter into the construction 

 of the occipital, sphenoid and parietal. In this respect the present 

 order of Reptiles seems to be most closely related to the Osseous 

 Fishes. 



In all the three orders composing this sub-class, namely, the 

 Sauria, Ophidia, and Chelonia, the occipital bone is furnished with 

 only a single condyle, which articulates with the first cervical ver- 

 tebra, and is usually formed by the coalescence of three ossicles, 

 namely, by the body of the occipital bone, which is always present, 

 and the two lateral occipitals. Between the two last is interposed 

 the supra-occipital plate completing- the foramen magnum from 

 above ; it is of small size in the Ophidians, but mostly large in the 

 Chelonia, where it projects backward into a pointed crest. In the 

 last named order, and in the Crocodiles, a pair of supra-laeral 

 occipital bones, as in Fishes, are intercalated between the others ; 

 they abut in the direction outward against the mastoid bone, in- 

 ternally against the petrous, and assist in forming the bony part of 

 the organ of hearing. The body of the sphenoid is broad and short 

 in the Chelonia, very elongated and narrow in the Ophidians, 

 whereas in most Sauria it projects forward in the form of a style. 

 The alae majores of the sphenoid are in the Ophidians and Saurians 

 perfectly membranous. There occurs here, however, a peculiar, 

 narrow, long and style-shaped bone, usually called the columella 

 (os tympanicum Bojanus, os suspensorium Nitzch) which ascends 

 perpendicularly like a small column from the inferior wings of the 



