OSSEOUS SYSTEM. 1 33 



in the Frogs with two large processes, one in the direction for- 

 ward and outward, uniting them with the supra-maxillary, 

 palatal and nasal bone, and the other, or posterior process, with the 

 os quadratum. In the Tailed Batrachia, as the Salamander, the 

 sphenoidal wings are not united to the supra-maxillaries, but 

 project forward into a free and pointed process ; in Acholotes they 

 unite with the vomer, but in the Siren are absent together with 

 the palatal bones. The temporal bone has only the articulating 

 portion of the petrous bone developed to form part of the cranium, 

 and this is let in between the circumjacent bones. The articulating 

 portion of the temporal, or what is called the os quadratum or tym- 

 panicum, is freely detached from the petrous, and consists mostly 

 of one, more rarely as in Proteus, of two pieces. It is united above 

 to the cranium by a suture, abuts inferiorly against the jugal bone, 

 and articulates with the lower jaw. The pair of parietal bones are 

 always distinctly present, but occasionally, as in Hyla and Bombi- 

 nator, separated by an interval or membranous fontenelle. The 

 two frontals of considerable size are very distinct in the Tailed and 

 in the Fish-like Batrachia, but are either absent in the Frogs or 

 anchylosed with the parietals. In front of the frontals, between 

 them and the intermaxillaries, certain bones are found, the homo- 

 logies of which it is by no means easy to determine. A pair of 

 ossicles placed in this situation in the Frogs and Pipa have been re- 

 garded by some writers as the nasal, by others as lateral ethmoidal 

 bones. In the Salamander, a pair of similarly placed, but smaller 

 bones, separated from each other in the middle line by the principal 

 frontals, have been regarded as particular bones under the name of 

 the anterior frontals, if they be not upon the other hand viewed as 

 ethmoids. A single azygos bone, which in many Batrachia and 

 also in Ccecilia appears as a small plate in front of the parietal and 

 frontal bones, and usually projects downward in the form of a sep- 

 tum, may be well considered as a middle ethmoidal. The lacrymal 

 bones are generally absent. The analogue of the jugal bone is 

 seldom met with, or is at all events not to be determined with cer- 

 tainty. In the Frog there lie in front of the apex of the body of 

 the sphenoid a pair of narrow transversely directed bones, which 

 are united to the superior maxillary, and by a small ascending 

 ramus, with the nasal bones j they may be regarded as the palatal 

 bones. In front of them is situated in the Frog a pair of bones of 

 considerable size provided with minute teeth, and which are proba- 

 bly the representatives of the vomerine. On the contrary, in the 



