136 



lines in breadth : the rest increase in length to the seventh, and then 

 again diminish. The external surfaces of the jjosterior ribs do not 

 present the deep excavations observable in those oi Das. Peba. The 

 sternal portions of the first pair of ribs are anchylosed to the ver- 

 tebral portions. The small processes that intervene between the 

 manubrium and the sternal ends of the clavicles in the young animal, 

 are afterwards anchylosed to the latter bone, and being joined to- 

 gether form a part superadded to tlie manubrium. This part is evi- 

 dently a rudimentary form of the Y-shaped bone placed anterior to 

 the rnanubriuvi of the Ornithorhynchus, which Cuvier regards as ana- 

 logous to the OS furcatorium of birds ; it thus aftbrds an additional 

 and very interesting example of the affinity of the Edentata to the 

 Munotremata, and supplies a step which was wanting in tracing the 

 recedence of the latter, in their remarkably constructed sternum, 

 from the mammiferous to the oviparous type of the Vertebrata. The 

 manubrium itself also presents a peculiarity observable in that of the 

 Monotremata, viz., a mesial longitudinal ridge on the anterior sur- 

 face. This appearance in the Ornithorhynchus is regarded by Cuvier 

 as indicative of an original division in the bone itself, ' Ossemens 

 Fossiles,' V. pt. 1 , p. 149 ; but I have examined the foetus of the nine- 

 handed species, and find that ossification commences in the manu- 

 brium by a single central nucleus, and not by two lateral depositions. 

 The other bones of the sternum appear, on an anterior view, to be 

 almost deficient, being wedge-shaped, with the apices anterior ; their 

 number is four, exclusive of the ensiform cartilage. 



"The pelvis in this skeleton presents all the peculiarities which 

 have been so well described by Cuvier : the ilia are of a prismatic 

 shape, not expanded as in Megatherium, but forming two short and 

 thick props or supporters to the armour. At the posterior part of 

 tlie pelvis the tuberosities of the ischin project in a similar manner, 

 and form similar props. It is evident from the form of the pubis that 

 only a small portion of what usually constitutes the symphysis is here 

 joined to its fellow, viz. the anterior angle ; and this approximation 

 to the structure of Birds is rendered more evident in a nearly allied 

 genus, Chlamyphorus, and in another edentate species, Myrmeco- 

 phaga didaclyla^ where the ossa pubis remain entirely separate. An 

 equally remarkable instance of the correspondence of this ])art of the 

 skeleton, — the pelvis, — with that of Birds, obtains in the great breadth 

 of the posterior part of the sacrum, the angles of which are anchy- 

 losed to the spines of the ischia, and convert the great ischiatic 

 notches into complete /ojrtmma. The cavity of the pelvis is very wide, 

 as may be inferred from the size of the young at the time of birth. The 

 brim measures in the antero-posterior diameter 2 inches 3 lines ; in 

 the lateral diameter I inch 3 lines: the outlet is of a triangular form, 

 and measures in the antero-posterior diameter I inch 6 lines ; in 

 the lateral diameter 1 inch 8 lines. The ischiatic foramen is of an 

 oval form, 1 inch in the long, and ^ inch in the short diameter. 



" The great size of the pelvis in this burrowing animal is the more 

 remarkable when contrasted with the peculiarly diminutive dimen- 

 sions of the same part in the Mole; in which it has been regarded as 



