52 The Ohio Naturalist. [Vol. IV, No. 3, 



COMPARATIVE CHART OF THE VERTEBRATE 



SKULL.- 



Charles S. Mead. 



In compiling the following chart, an attempt has been made to 

 show the history of the cranial bones in the different classes of 

 vertebrates. To make it general as well as specific from one to 

 four types are given under each class, and where possible, an 

 unspecialized and a highh- specialized form have been taken. As 

 a rule, the same bone occurs in the difi^erent classes of vertebrates, 

 but it may fail to develop, as in the Amphibians, or several bones 

 maj^ fuse to form larger elements, as in the Mammals, and it is 

 the purpose of this chart to show these irregularities. 



In the higher types, especially the birds, there is a great ten- 

 dency for bones that are separate in the immature stages to fuse 

 in the adult, the sutures being oblilerated. In Lacerta and the 

 Amphibia manj- elements that are indicated as bones remain carti- 

 laginous. Where two or more bones in one type fuse to form 

 one bone in another type the line between them has been omitted. 



In the Urodeles, Ophidians, and Chelonians no particular type 

 has been taken. 



Different authors have used different names for the same bone 

 in the same class or different classes, or the same name ma}- be 

 used for as many as four different bones. Below is given a list of 

 synonyms : 



Jugal, malar, zygoma, zygomatic. 



Ouadrato-jugal, zygomatic. 



Squamosal, supratemporal of Ophidians. 



Supra-angular, surangular. 



Coronoid, coronary. 



Lacrymal, supraorbital. 



Sphenotic, postf rental. 



Prootic, petrosal. 



Periotic, petrosal of Mammals. 



Epipter^-goid, columella. 



Transverse, ectopterygoid, transversum, transpalatine. 



Pterygoid, ectopter^-goid. 



Mesoplerygoid, entopterygoid. 



I\Ie.sethmoid, ethmoid, supra-ethmoid, median ethmoid. 



Ectocthmoid, ectethmoid, parethmoid, lateral ethmoid. 



Turl)inal, ectoethmoid. 



Maxilla, maxillary, supermaxilla, superior maxilla. 



Premaxilla, intermaxilla, anterior maxillary, incisive. 



-From the Zoological laboratory of the Ohio State University. 



