96 Elementary Zoology. 



consists of a rod of cartilage, ossified near to its articulation into 



the articulare, and at its junction with the corresponding half, 



the Mentomeckelian : along the shaft it is covered by membrane 



bone, dentary ; besides these, there is the hyoid apparatus. 



Two long processes, one on either side, connect the plate-like 



hyoid with the skull wall. Posteriorly a pair of ossified rods, the 



thyrohyals, represent one of the branchial arches proper. 



It may assist the remembering of this complicated series of 



bones if they be arranged in accordance with the elements of 



the skull to which they severally belong, the membrane bones 



(distinguished by italics) being.placed in their proper relations 



to the rest — 



BRAIN-CASE. 



Cartilage Bones. Membrane Bones. 



Exoccipitals. Parasphenoid. 



Sphen-ethmoid. Frontoparietals. 



Maxillce. 

 Premaxilla. 



CAPSULES OF SENSE ORGANS. 

 Pro-otic. Squamosal. 



Nasals. 

 Vomers. 



FIRST VISCERAL ARCH 



Quadrate.' 



Quadrato-jugal. - 



Pterygoid.' 



Palatine.'' 



Articulare. 



Mento-meckelian. Dentary. 



SECOND VISCERAL ARCH. 

 Columella. 



FOURTH VISCERAL ARCH. 

 Thyrohyal. 



■ ' The degree in which the quadrate is ossified among frogs varies much. 



' This is marked as a cartilage bone in my figures. More probably it 

 is a membrane bone ; but see following footnote. 



' These are marked in the figures as cartilage bones. So they have 

 been said to be. But perhaps the prevailing opinion is in favour of regard- 

 ing them as membrane bones grafted on a cartilaginous substratum. I am 

 unwilling, however, to attempt to decide between Prof. Parker (who 

 colours these bones yellow, by which he means cartilage bones) and others. 

 The fact is, it is not always easy to draw a hard-and-fast line between 

 endosteal and ectosteal ossifications. 



