Miscellaneous, 391 



entire size of the animal it shows a more gigantic development than 

 in any other mammal. Exteriorly the malleus unites by an 

 articulation with the squama temporalis at a point which appears to 

 be depressed by the externally projecting hinder extremity of the 

 zygomatic bone*. Nevertheless this union does not take place 

 directly, but by means of a smaU acutely triangular ossicle, widen- 

 ing from before backwards, which, on careful examination, proves 

 to be nothing but a portion of the incus which is amalgamated with 

 the malleusf. 



But if the malleus be examined on its upper surface, a distinct 

 suture appears to be present in places at the point where the long 

 process unites with the malleus ; and this leads us to expect that in 

 very young animals a dividing suture will be found here. 



At any rate it is of importance to the question of the interpreta- 

 tion of the quadrate bone in birds, that in the full-grown Tachy- 

 gJossus there is a bone, consisting originally of three or iowx sepa- 

 rate pieces, which effects an articular union of the squama temporalis 

 with the OS pterygoideum and (at an earlier period) with the lower 

 jaw. 



In Ornithorhynchus, in which the incus remains separate through- 

 out life, the os tympanicum unites directly by the malleus with the 

 squama temporalis ; nevertheless it is to be observed that the incus 

 situated above it is likevsdse united with the squama temporalis, 

 which is the cause that, in this genus, it is difficult to remove the 

 auditory ossicles in connexion. 



Here, therefore, we see, in the Monotremata, that a bone composed 

 of two or more pieces presents the same articular connexions as the 

 OS quadratum in birds, that by these pieces, through the os tym-pa- 

 nicum, is effected the union with the os pterygoideum and the iimer 

 angular process of the lower jaw, whilst that with the squama tem- 

 poralis is effected by the malleus and incus, or by the incus alone. 

 The question stiU remains to be solved, in the young Monotremata, 

 whether the long process of the malleus (occurring as a distinct 

 bone, and, in part, representing a part of the os tympanicum of the 

 higher MammaHa) at any time forms a condyle corresponding to 

 the outer cavity of the articular process of the lower jaw in birds. — 

 Monatsber. Berl. Akad. der Wiss. Dec. 5, 1867, pp. 779-781. 



* To me the interpretation of this peculiar bone, which attaches itself 

 like a scale upon the squama temporalis, given by LauriUard and Duver- 

 noy seems to be quite correct, although it is remarkable that it assists in 

 the formation of the cranial cavity, which, indeed, induced Mr. Owen not 

 to agree in this interpretation, without, however, giving a better one 

 (Monotremata, Cycl. of Anat. & Phys. p. 7). I have been able to investigate 

 this bone upon a very beautiful dissected skull, most kindly communi- 

 cated to me by Professor Keferstein of Gottingen. 



t That this small intermediate bone, which effects the articular union 

 with the squama tempm-alis, is a portion of the incus was first made plain 

 to me by a kind communication from my friend Flower, whom I induced 

 to investigate this subject, and who wrote to me that he had foimd in a 

 young skidl of Tachyr/lossus the incus, which had previously been entirely 

 ofverlooked, and which would only subsequently be amalgamated with the 

 malleus, but was then distinctly to be recognized. 



