390 Miscellaneous. 
In a young Halmaturus Bennettii, measuring (without the tail) 
85 millims., the os tympaniewm forms a ring broken through 
before and behind, just asin 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. 
From 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 still 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 Ornithorhynchus 
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.— 
Monatsber. Berl. Akad. der Wiss. Nov. 21, 1867, pp. 725-729. 
‘On the Tympanic Bone and Ossicles of the Ear in the Monotremata, 
in connexion with the question of the interpretation of the Quadrate 
Bone in Birds. By Professor W. Purmrs. 
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 
skull 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 tympanicum 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 pterygoideum, 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 
