82 LECTURE IV. 



bones which project freely backwards from the occiput of theFistularia, 

 with the dermal skeleton : the strong temporal muscle is attached to 

 the two surfaces, divided by the ridge on its inferior part : it is 

 movable up and down upon its anterior ligamentous union. In its 

 relative position and functions, it combines the characters of post- 

 frontal and mastoid ; and, since the basilar elements of these cranial 

 vertebi'fe are confluent, and their spinal elements also form one piece, 

 {Jig. 29. 4, il), we may here also have an example of a similar con- 

 fluence of the parapophyses of two distinct vertebrae. The mid- 

 frontal {ib. 11 ) constitutes the anterior part of the epicranial bone, 

 which is connected with the post-frontal and the cartilage perforated 

 by the olfactory nerves and representing the pre-frontals. 



A more remarkable and less easily determinable bone is that tri- 

 angular horizontal plate {ib. 15), the broad posterior base of which is 

 attached by ligament to the mid-frontal, to the post-frontal, and to 

 the pre-frontal processes of the palato-maxillary arch ; whilst the 

 apex forms the anterior extremity of the cranium, and supports at its 

 under part two vertical sharp-pointed teeth. I originally compared it 

 to the combined nasal and intermaxillary bones ; but I now regard 

 the cranial structure of the MurcEnidce, in which the intermaxillaries 

 ai"e absent, and the nasal bone dentigerous, as giving the true key 

 to the special homology of the bone in question. This nasal bone 

 is movable, up and down, upon its basal joint, and reminds one of 

 the similarly movable and attached appendage in the Callorhynchus, 

 the free end or apex of which is beset at its under part with several 

 small teeth. 



The triangular vomerine, or prefronto-vomerine, cartilage closes the 

 anterior and under part of the cranial cavity, and supports the origins 

 of the olfactory nerves, which perforate it in their passage to the 

 cartilaginous nasal capsules. 



Each ramus of the lower jaw {Jig. 27. 32) is composed of an 

 articular and a dentary piece, the latter anchylosed together at the 

 symphysis, and completing the inverted tympano-mandibular arch. 

 The articular piece is a simple slender plate, strengthening the outer 

 part of the articular concavity of the jaw, and closing the outer 

 groove of the dentary, along which it is continued forAvards to near 

 the symphysis, where it ends in a point. The articular trochlea is 

 formed by a persistent cartilage, which penetrates the cavity in the 

 dentary, escapes from the fore-part of the groove on the outer surface 

 of the dentary, and joins its fellow, in a small cartilaginous mass, 

 which fills the hollow in front of the symphysis. The dentary piece 

 has the notched and trenchant dentinal plate anchylosed to it, and 

 sends up a strong coronoid process. 



