128 Scientific Intelligence. 



in a vertebra forming the anterior extremity of the series ; and the 

 typical condition of the prefrontals, so well shown in fishes and saurians, 

 is marked in mammals by the enormous development of the capsules 

 of the orofan of smell anterior to them, which become ossified and par- 

 tially anchylosed to the compressed, shrunken and coalesced prefrontals; 

 the whole forming the composite bone called " rethmoid" in anthro- 

 potomy. The vomer, or body of the nasal vertebra, has undergone 

 an analogous modification to that which the terminal vertebra of the 

 tail presents in birds ; whence its special name, referring to the like- 

 ness to a ploughshare, in human anatomy. The spine, or nasal bone, 

 is sometimes single, sometimes divided, like the frontal, the parietal 

 and the supraoccipital bones. Their special adaptive modifications 



,in 



have obtained for them special names. 



The haemal arches corresponding with the above neural arches re- 

 tain most of their natural position and proportions, as might be expect- 

 ed, in fishes ; they are called the scapular, hyoid, mandibular, and 

 maxillary arches. The pleurapophysis of the occipital vertebra is the 

 scapula, and is commonly attached by a head and tubercle to the cen- 

 trum and parapophysis of its proper occipital vertebra. 



The hyoid arch is suspended by the medium of the epitympanic to 

 the mastoid parapophysis of the parietal vertebra, the epitympanic 

 fishes, intervening and separating the hsemal arch from its proper ver- 

 tebra, just as the squamosal intervenes to detach the tympanic pleura- 

 pophysis of the mandibular arch from its proper vertebra in mammals; 

 which vertebra the squamosal attains in man by articulating with the 

 process representing the coalesced postfrontal. In return, we find the 

 hyoidean arch resuming its normal connexions in many mammalia, the 

 stylo-hyal element being directly articulated to the mastoid : in man 

 the large petrosal capsule intervenes, and contracts that anchylosis with 

 the proximal or pleurapophysial element of the hyoid arch, which has 

 led to the description of the stylohyal as a process of the temporal 

 bone, in works on human anatomy. 



In fishes, the tympanic, which is the true pleurapophysis of the 

 mandibular arch, always articulates with the postfrontal, besides its 

 accessory joint with the mastoid. The maxillary arch is articulated 

 by its pleurapophysis, the palatine bone, with the centrum and neu- 

 rapophysis (vomer and prefrontal) of the nasal vertebra. This is the 

 normal and constant point of suspension of the maxillary arch; other 

 accessory attachments to ensure its fixation and strength are succes- 

 sively superinduced upon this primary and essential one. Through 

 this knowledge of the general homology of the palatine, an insight 

 was gained into its singular disposition in man, creeping up, as it were. 

 into the orbit, to touch the pars plana of the ethmoid; this secret 

 affinity with the modified neurapophysis of the nasal vertebra become* 

 intelligible by a recognition of its relations to the general type of the 

 vertebrate skeleton, by its determination as the rib or pleurapophys' 5 

 of the nasal vertebra, and therefore retaining, as such, more or less o 

 its essentia! connexion with the centrum (vomer) and neurapophy^ 

 (aethmoid or prefrontal) of the nasal vertebra throughout the vertebrate 

 series. 



