390 Miscellaneous. 



In a young Eulmaturus Bennettii, measuring (without the tail) 

 85 millims., the os tympanicum forms a ring broken through 

 before and behind, just as in the developed state in the Monotre- 

 mata. The anterior and stronger part of this ring divides into a 

 fork above, and embraces Meckel's process from without and behind, 

 whilst beneath it fits exactly with a convexity upon the inner sur- 

 face of the ascending portion of the lower jaw, and with a smooth 

 articular surface into the upper concave surface of the incurved 

 angle of the jaw. 



I find the conditions exactly similar in older examples of Didel- 

 phys aurita, only that the tympanic bone is already separated by a 

 thin layer of connective tissue from the angle of the lower jaw. 



Fi'om this the peculiar characteristic formation of the angle of 

 the lower jaw in the lower Mammalia is at once explained ; its in- 

 wardly projecting portion corresponds, as a provisional articular 

 process, with the permanent inner articular process of Birds. 



It is possible, and appears to me even probable, that the malleus 

 in Birds contributes to the formation of the quadrate bone, as in 

 Birds there is stiU a second outer articular cavity, no part corre- 

 sponding to which exists in the Marsupialia. This will probably 

 find its explanation among the Monotremata, as in OrnithorTiynchus 

 a peculiar external process of the lower jaw occurs, corresponding 

 in position to the outer articular process in Birds ; and I hope soon 

 to be able to make further communications upon this point. — 

 Monatsher. Berl. Akacl. der Wiss. Nov. 21, 1867, pp. 725-729. 



On tlie Tympanic Bone and Ossicles of the Ear in the Monotremata, 

 ■ in connexion with the question of the intetpretation of the Quadrate 

 Bone in Birds. By Professor W. Peteks. 



My hope of obtaining very young Monotremes, and by their inves- 

 tigation solving, as I expected, the question of the homology of the 

 quadrate bone of birds with the tympanic bone, has not been ful- 

 filled ; but yet, from the examination of a not completely developed 

 skuU. of Tachyglossus hystrix, for which I am indebted to the kindness 

 of Dr. Mobius, and from that of a still younger skull of Ornithorhyn- 

 chus belonging to the Zoological Museum of Berlin, some results have 

 been obtained which seem to me worth communicating. 



The OS tympanicimi of Tachyglossus is, indeed, at a later period 

 amalgamated with the long process of the malleus, but the boundary 

 between them may still be distinctly recognized. It then forms a 

 half ring, the thinnest middle part of which is applied directly to the 

 OS pterygoidemn, and at the spot which lies nearest to the apex of 

 the long process of the malleus it is but little widened. But in the 

 young specimen now before me, this entire region is the broadest of 

 the ring, and moreover it is furnished on its lower free surface with a 

 slight convexity, which corresponds to the inner concavity of the 

 small angle of the lower jaw, and which, in all probability, and 

 judging from the conditions in the Marsupials, was previously united 

 like a joint with this cavity. The extraordinary size of the long 

 process of the malleus is likewise remarkable ; in proportion to the 



