410 



HARRIS HAWTHORNE WILDER ON 



otic capsule. It is (lifficult to (leterniiiie. in a piece of this shape, the location of the proc- 

 esses cited by aiitiior.s in their description of the ([iiadrate of other Aniphil)ia. The p(js- 

 terior lateral extension which runs along the side of the bone is probably the otic process, 

 and tlie narrowed part, or its posterior prolongation, tlie pedicel. Of the two processes 

 which form the isthmu.s and become applied to the trabecula, the anterior one may possi- 

 bly be the ascenchug process. A slight angle seen in the anterior margin is doubtless the 

 rudiment of the " cartilaginous pterygoid " found in most Urodeles, the extension of which 

 to the antorbital process would form the palato-pterygoid arch wdiich is wanting here. 

 Aside from its attachment to the trabecula, the quadrate, osseous and cartilaginous, enters 

 into more or less complete attachment to four bones. As described al)ove, two processes 

 of the pi'o-otic form quite definite articulations with the (piadrate cartilage, the \entral 

 one receiving an articular surface formed by a thickened piece of cartilage in the middle 

 of the posterior margin, and the dorsal one being applied along the inner edge of the otic 

 process. The para(iuadrate overlaps it externally, and tlie outer posterior corner of the 

 palato-pterygoid fits into a gi'oove in the inner side of the articular process and overlaps a 

 raised area of the quadrate cartilage. The cartilaginous articulare of the mandilde forms 

 a movable articulation with it. 



In determining the position of an isolated osseous quadrate it may be remembered 



tliat the side showing the liollow groove is 

 internal, that the larger end is anterior, and 

 that the broader, plainer surface is dorsal. 



5 and 6. paraquadratum and opercu- 

 lum. These elements, oi wdiich the first is a 

 dermal bone, and the second an ossification 

 of a detached portion of the otic capsule, are 

 closely connected topographically and joined 

 to one another by a strong ligament whicli 

 unites processes in each bone mutually 

 directed toward the other. The paraquadra- 

 tum, the shape of which suggested a boom- 

 erang to Huxley, attached in its normal man- 

 ner to the little discoidal operculum, presents 

 the appearance given in figure 1 1. When in 

 place upon the skull, the para(|uadrate lies 

 along the outer side of the otic region, form- 

 ing the two sides of the pentagonal outline 

 of the skull designated above as " paraquad- 



EXTLRNAL. 



Fig. 11. Right paraquadratiiiu 

 Two views, x 3. 



INTlRNAl 



and (iperculuni. 



