ON THE VERTEBRATE SKELETON. 207 



The high repute which M. Agassiz has so justly earned in ichthyotomy 

 renders the accession of his name in support of Drs. Hallmann, Reichert, 

 and Kdstlin's determination of the bone in question, one to which those able 

 homologists and their followers will naturally attach great weight, and which 

 indeed has caused me to pause and retrace more than once, and with the 

 utmost pains and care, every step in the series of comparisons which have 

 finally brought conviction of the accuracy of the Cuvierian determination of 

 no. s in fishes. 



I am not aware that any anatomist has replied to the objections to the 

 Cuvierian view propounded by M. Agassiz. Drs. Hallmann and Kdstlin, 

 who have published the most elaborate monographs on the temporal and 

 other bones of the skull since the time of Cuvier, concur entirely with the 

 learned Swiss naturalist. Dr. Reichert, in giving the name of ' squama tem- 

 poralis' to no. s, and that of 'processus temporalis posterior' to its process, 

 transfers the name ' processus mastoideus' to the paroccipital (no. 4, fig. 5)*. 

 It becomes then necessary to consider the arguments of M. Agassiz in favour 

 of the homology of no. 8. in fishes with the squamosal no. 27 in mammals. 

 In the valuable monograph on the osteology of the pike (Esox) in the 15th 

 'Livraison' of the ' Recherches sur les Poissons Fossiles,' the author says 

 (p. 66), " Un os de la tete place entre le frontal posterieur, le frontal prin- 

 cipal, le parietal, la grand aile sphenoidale et l'occipital lateral, ne saurait 

 jamais etre envisage comme correspondant a l'apophyse masto'idienne du 

 temporal. D'apres ses liaisons, je crois done qu'il faut envisager le masto'idien 

 de Cuvier comme l'analogue de Y.ecaille du temporal ou comme le temporal 

 proprement dit. C'etait deja l'opinion de Spix, qui est tombe juste sur ce 

 point" To this I reply that, in regard to the connections of the mastoid, those 

 with the parietal, alisphenoid and exoccipital, are more constant than that 

 with the frontal, which is interrupted in mammalia by the interposition of 

 the expanded squamosal, peculiar to that class ; but the mastoid retains its 

 piscine connection with the postfrontal in many reptiles and some birds. On 

 the other hand, the union of the squamosal with the frontal is by no means 

 a constant character in mammalia : it is rarely found in the orang, still more 

 rarely in man, never in the cetacea and monotremes, nor in certain ruminants, 

 nor in the myrmecophaga, &c. The connection of the mastoid with the 

 frontal is more common than is the connection of the squamosal with the 

 exoccipital. It is a bold leap to take from the mammal to the fish in the de- 

 termination of a variable bone like the squamosal : nevertheless, I would re- 

 quest the unbiassed reader to glance at fig. 12, whilst he reads M. Agassiz's 

 precis of the character of the squamosal above cited, and see how far no. s de- 

 viates from it, save in regard to the frontal connection. Spix, who appears 

 not to have traced the beautiful gradation of the mastoid in the mammalia, 

 and who was unacquainted with the decisive step to its normal condition in 

 the oviparous vertebrates made by the monotremes, — and who was influenced, 

 therefore, by seeing that bone in higher mammals pushed back from any con- 

 nection with the alisphenoid and postfrontal by the interposed squamosal, 

 which usurps these connections and combines them with others, as with the 

 parietal and tympanic, which the mastoid (no. s) presents in fishes, — not un- 

 reasonably concluded that no. s represented the squamosal in that class; and 

 it is probable that M. Agassiz, who received his anatomical rudiments at 

 Munich, and was early engaged in describing the fishes collected in Brazil by 

 the author of the ' Cephalogenesis,' might have derived a bias in favour of this 

 view which prevented his assigning their due value to the connection of no. s 

 in fishes with the paroccipital, and its contribution to the otocranial cavity. 

 * Op. cit. tab. iii. figs. 9 and 13, p, q. 



