210 REPORT— 1846. 



the maxillary with the tympanic, and marked z ml in fig. 7, taf. i. of Dr. Kall- 

 mann's monograph ? If Cuvier had been correct in regarding no. 8 as the 

 squamosal, the name ' jugal' ought to have been transferred from the lower 

 zygoma to the upper one connected with such squamosal in the macaw : and 

 with a like consistency the name 'jugal' ought to have been retained for the 

 suborbital chain of dermal bones in fishes, to which it had been applied by 

 GeofFroy St. Hilaire, and to which it has been restored by M. Agassiz. But, 

 in truth, there may be clearly discerned in the beautiful modification which 

 has been adduced from the Psittacidce, a proof of Cuvier's erroneous homo- 

 logy of the bone no. 8 in the class of birds, and at the same time of his 

 accurate homology of the same bone in that of fishes. 



Is there no significance in the fact of the bone anterior to the orbit, which 

 we call lacrymal in man down to the lowest reptile, being constantly per- 

 forated by a mucous duct ? Can we not recognize in this function and 

 glandular relation, as in the commonly thin scale-like character of that bone, 

 and its connections in front of the orbit, the repetition of the characters of 

 the largest, most anterior, and most constant of the suborbitals in fishes ? If 

 the rest of that chain be sometimes wanting, but more commonly present in 

 that class ; if it should present the condition occasionally of a strong conti- 

 nuous bony inverted arch, spanning the orbit below from prefrontal to post- 

 frontal, as in the right orbit of the Hippoglosstis and the left orbit of Rhombus; 

 ought we to lose our grasp of the guiding thread of ' connections ' by being 

 confronted with a repetition of that condition in the skulls of certain birds, 

 caused by a continuous ossification from the lacrymal to the post-frontal, 

 seeing that a diverging bony appendage of the maxillary arch, unknown in the 

 class of fishes, has there established a second and true ' zygoma' below the 

 suborbital one ? The extension of the ossification from the post-frontal crus 

 of the suborbital arch to the mastoid is, in truth, a beautiful repetition of an 

 ichthyic cranial character, not unknown however in the reptilia ; and whilst 

 it adds a proof of the mastoidal character of no. 8 in the bird, it reflects 

 reciprocal confirmation of the accuracy of Cuvier's determination of that 

 bone in fishes. 



The true signification and homologies of the bones in that interesting 

 class could never have been elicited from an exclusive study of it, however 

 extensive, detailed or profound ; nor will the feeble rays reflected from an- 

 thropotomical reminiscences lend sufficient light in their determination : they 

 can be clearly discerned only by the full illumination of the beams concen- 

 trated from all the grades of organic structure. M. Agassiz, descending to 

 the determination of the squamosal in fishes from its characters in man, con- 

 cludes that it must be the bone no. 8, fig. 5, because that bone takes part in 

 the formation of the inner as well as the outer walls of the cranial cavity. But 

 this protective function is an exceptional one in the squamosal (fig. 6, 27); 

 it is peculiar to that bone only in one class, and, as we have seen, is not con- 

 stant even there ; whilst, on the other hand, the mastoid is recognizable 

 from the inner surface of the cranial walls of the highest mammal (in the 

 human cranium where it is impressed with the fossa sigmoidea, fig. 6, s), and 

 in a still greater degree in that of the lowest mammal (Echidna, fig. 12, s) ; 

 whilst in almost every mammal, by its coalescence with the outer surface of 

 the petrosal, it closely repeats the protective character in relation to the ex- 

 ternal semicircular canal, which it presents in fishes, — a function which is 

 altogether foreign to the squamosal in every mammal. I have dwelt thus 

 long, perhaps tediously, and it may be thought unnecessarily, on the true 

 characters and homologies of the petrosal and mastoid. But their determina- 

 tion is essential to, and, indeed, involves that of the squamosal and other 



