782 MR. W, A. FORBES ON THE [June 21, 



examined by me, and all agree closely in their tracheal structure 

 with A. ma'ntelli. My pecimeiis of J. australis and A. oweni (two) 

 agree together in having the last three tracheal rings incomplete 

 posteriorly ; whilst in A. mantelli and A. haasti, of which I have 

 seen only single specimens, the last ring alone is incomplete. 



In the Ciisuariidce we meet with peculiarities in the structure 

 of the bifurcating trachea not existing in the other " Ratitse." 

 In Casuarius galeatiis (figs. 5, 6, p. 783) the trachea is somewhat di- 

 lated for the terminal inch or so of its extent, tranverseW and also 

 posteriorly. The last tracheal rings (for a number varying in dif- 

 ferent specimens, in the specimen in question 12, in another 23) are 

 incomplete in the middle Hne behind, though the posterior ends 

 are closely approximated together '. 



These rings are tolerably uniform in breadth posteriorly, tapering 

 only somewhat at their extremities ; the iuterannular intervals are 

 mere chinks. Anteriorly, however, the rings being dilated in the 

 median line and attenuated laterally, theintervals are better developed. 

 The last 5 or 6 rings are rrore and more curved downwards anteriorly, 

 whilst their posterior moieties are somewhat dilated, their ends 

 gradually receding more and more from each other in the middle 

 line. There is no trace of apessulns. 



The first bronchial semirings much resemble the last tracheal 

 rings, their anterior extremities being closely approximated together, 

 and their posterior ones dilated, and somewhat pointed, terminally. 

 The second, third, and fourth bronchial semirings are simple 

 cartilaginous hoops, tolerably deep, separated only by narrow in- 

 tervals, and, as usual, completed internally by a membrana tympani- 

 formis. The fifth, sixth, and seventh are similar but longer semi- 

 rings, the sixth and seventh being dilated anteriorly. The suc- 

 ceeding rings are similar but quite simple hoops, never forming 

 anywhere complete circles. 



There is no trace of any intrinsic muscles. The sterno-tra- 

 cheales are inserted on the trachea at about tiie twelfth ring from the 

 last. Anteriorly they expand on the tracheal wall, and are in 

 contact with each other over the middle line, as is also the case in 

 BromcBUS, though not in the other three genera. A small part of 

 each muscle runs to be inserted into the posterior wall of the trachea 

 near the margin. The lateral muscle of the trachea passes between 

 these two portions of the sterno-trachealis of its side, but does not pass 

 down further than the commencement of the tracheal tympanum. 



^ Between the extremities of eacli impevfect tracheal ring runs a short hand 

 of connective and elastic tissue, with the fibres running transversely. These 

 extend the whole length of the trachea, and when well developed have the ap- 

 pearance of a longitudinal band running along tlie middle line of the tube 

 posteriorly. By the contraction of these fibres, the ends of the tracheal rings, 

 where these are incomplete, or their more slender middle portions where per- 

 fect, are drawn together, and pressed into the interior of the tube, so forming 

 what at first sight looks very much like a longitudinal, though incomplete, tra- 

 cheal septum, such as is found in some Prooellariidte and other birds. In con- 

 sequence of this structure, a transverse section of the tracheal tympanum poste- 

 riorly presents two strong convexities separated by a median concavity. 



