TIIK SKELETON OF THE VERTEBUATK IIKAU. 179 



111 all tin forms, I lieliove that traces of tlie intermediate or 

 temporal centrum may be detected, either in tlie cartila<,'inous 

 or osseous condition. In fishes, more or less of the primordial 

 cartilage remains above the junction of the occipital centrum, 

 post-sphonoidal centrum, and tem]>oral neurapnphyses ("petro- 

 sals"), and covered more or less internally, or towards the 

 cranial cavity, by the internal prolongations of the occipital 

 centrum, and of the temi)oral and post-sphenoidal neurapo- 

 jihyses. Tlie peculiar canal for the muscles of the orbit 

 existing in certain fishes, and which is roofed over principally 

 by the " petrosals," or temporal neura])Ophyses, appears to be 

 hollowed out principally in the primortlial temjjoi-al centiiim, 

 and to be lined by its constituent cartilage. The peculiar Y- 

 sliaped bone met with in the pike, perch, and salmon, marked 

 9^ by Professor Owen, and * by Hallman, and considered by 

 the former as that portion of the pre-sphenoidal centrum which 

 results from the ossification of the corresponding central por- 

 tion of the notochord, appears to me to be a central element, 

 but referable rather to the post-sphenoidal or temporal than 

 to the pre-sphenoidal segment. For, in the first place, it may 

 be questioned whether the corda dorsalis of the fish reaches 

 the region of the pre-sphenoid ; and, in the second place, if I 

 am correct in my determination of the post-sphenoidal and 

 temporal neurapophyses of the fish, the two ascending limbs 

 of this bone abut against these latter elements, and are not at 

 all connected with the pre-sphenoidal neurapophyses. As, 

 moreover, these ascending limits of the bone in question are 

 more intimately connected with the bones which Professor 

 Owen considers to be the ali-sphenoids, but which I must hold 

 to be the inferior tempoi-al neuraitophyses, I am inclined to 

 conceive it an ossified portion of the temporal centrum. 



With regard to the bone termed by Hallman os innomi- 

 natum, which is small but well marked in the carp, and larger 

 in the perch, and which Professor Owen cousidei-s to be the 



