BY DR. E. W. SHUFELDT, C.M.Z.S, 103 



edition of Flower's Osteology of the Mammalia. To be 

 sure, there are a great many special monographs on the 

 skeletology of mammals that are constantly consulted in this 

 line of investigation; but these are not in the same class 

 with a manual on the subject — one that essays to give suc- 

 cinct accounts of the bones of the skeleton of mammals in 

 general, such as do the two works mentioned above. 



The Skull in the Adult Duckbill: — As has already been 

 pointed out by a number of writers on this part of the skele- 

 ton in Ornithorhynchus, the sutures among the several bones 

 composing it are almost entirely obliterated in the adult, and 

 this is distinctly the case with respect to the skulls of these 

 specimens in the Army Medical Museum. Owen gives us the 

 superior view of the skull of a young Duckbill, wherein the 

 sutures among the bones are in evidence, and it is a very 

 useful cut. (Fig. 205, p. 321). 



At d in Figures 5 and 9 we have a full view of the much 

 discussed "dumb-bell shaped bone" of authors. Owen speaks 

 of this as a "small prenasal ossicle" (p. 322) ; while Flower 

 states that "There is a distinct median dumb-bell shaped 

 "ossification in the triangular interval between the diverging 

 "premaxillary bars, placed in front of the anterior extremity 

 "of the mesethmoid cartilage, on the palatal aspect of the 

 "jaw. This bone is not the homologue of the so-called pre- 

 "nasal of the Pig"; but "it corresponds with that part of 

 "the intermaxilla which lies between the incisive canal and 

 "the mesial palatal suture." (6) (Pp. 243, 244.) 



The distal ends of the premaxillaries are turned inwards, 

 toward each other and almost at right angles, the interval 

 being about a centimetre. This interval is spanned by a 

 strong, flat ligament, and it is joined, posteriorly, by another 

 ligament, running from the dumb-bell-shaped bone in the 

 median line as shown in Figure 5 of Plate XIX. 



On the ventral aspect of the anterior moiety of either 

 maxillary, there is, upon either side, a very shallow, longi- 

 tudinal groove about two centimetres in length. Horny, 

 pseudo teeth are attached to either of these as shown in 

 Figure 9 of Plate XX. The far more formidable pair is 

 situated considerably further back, each occupying the ven- 

 tral surface of a Ttiaxillary upon either side. In the dried 

 skull these structures can easily be pried off, whereupon 



(6) TURNER. W.— "The dumb-bell-shaped Bone in the Palate of Orni- 

 "thorhynchus compared with the prenasal Bone of the Pig." (Journ. 

 Anat. Phys., XIX., 1885, p. 214.) 



ALBRECHT, P. — "Sur la Fente Maxillaire et les quatre Os Intermaxil- 

 "laires de rOrnithorynque." Bruxelles, 1883. 



