136 



lincs in bieacitli : the ręst increase in length to theseventh, and thcn 

 again diminish. Tlie external surfaces of tlie posterior ribs do not 

 presenl the deep excavations observable in those ot Das. Peba. The 

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

 tebral portions. The small processes that intervene between the 

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

 are after\vards anchylosed to the latter bone, and being joined to- 

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

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

 the manubrium of the Ornithorhynchus, vvhich Cuvier regards as ana- 

 logous to the os furcalorium of birds ; it thus afibrds an additional 

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

 Monotremata, and supplies a step which was \vanting in tracing the 

 recedence of the latter, in their remarkably constructed sternum, 

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

 vianubrium itself also presents a peculiarity observable in that of the 

 Monotremata, v\z., a mesial longitudinal ridge on the anterior sur- 

 face. This appearauce in the Ornithorhynchus is regarded by Cuvier 

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

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

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

 brium by a single centrai nucleus, and not by tvvo lateral depositions. 

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

 almost deficient, being wedge-shaped, vvith the opices anterior j their 

 nuinber is four, exclusive of the ensiform cartilage. 



"The petvis in this skeleton presents all the peculiarities which 

 have been so \vell 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 

 the pelvis the tuberosities of the ischia project in a similar manner, 

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

 only a small portion of vvhat usualiy constitutes the symphysis is here 

 joined to its fello\v, 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 didactyla, vvhere the ossa pubis remain entirely separate. An 

 equally remarkable instance of the correspondence of this part of the 

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

 of the posterior part of the sacrum, the angles of \vhich are anchy- 

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

 notches into complete/ora7nJ7ia. The caviiy of the pelvis is very vvide, 

 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 1 inch 3 lines: the outlet is of a triangular form, 

 and measures in the antero-posterior diameter 1 inch 6 lines ; in 

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

 ovaI form, I inch in the long, and į inch in the short diameter. 



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

 remarkable when contrasted with the peculiarly diminutive dimcn- 

 aion^of the šame part in the Mole; in \vhich it has been regarded as 



