130 ON THE "dumb-bell-shaped" BONE IN ORNITHORHYNCHUS, 



interpretation of the bone as a ' prenasal osvsicle.' This view was 

 adopted by Flower in the earlier editions of the 'Osteology of the 

 Mammalia' (5, p. 219), where the bone is referred to as placed 

 in, or in front of, the anterior extremity of the mesethmoid 

 cartilage, and apparently corresponding to the so-called ' pre- 

 nasal ' of the pig. In 1883 Albrecht (7) again advocated the 

 older (intermaxillary) view of the bone mainly upon reasons 

 derived from a study of the normal and pathological development 

 of the premaxilla in other mammals. The contentions of this 

 author were in 1885 supported by Sir William Turner, who 

 devoted a paper in the Journal of Anatomy and Physiology (8) to 

 a critical examination of the prenasal and intermaxillary theories 

 respectively. His reasons for adhering to the latter are in part 

 founded on his own observations upon the region by means of 

 special dissection. In the edition of the ' Osteology of the 

 Mammalia' published during the same year, 1885, Professor 

 Flower (with Dr. Gadow) explicitly gave up the prenasal theory 

 in favour of the intermaxillary as advocated by Albrecht and 

 Turner. But in the descriptive passage referring to it an 

 extremely misleading description is given of the bone as "placed 

 in front of the anterior extremity of the mesethmoid cartilage in 

 the palatal aspect of the jaw." This statement is indeed quite 

 inconsistent with one of Turner's points of contrast between the 

 dumb-bell bone and a true prenasal, viz., that the latter is (and the 

 former is not) " placed in front of the vomer and mesethmoid 

 cartilage," And in point of fact the dumb-bell bone is entirely 

 ventrad of the cartilaginous septum and far behind the preaxial 

 end of the latter. 



The latest contribution to the literature of this subject that I 

 am aware of (apart from the paper in the Macleay Memorial 

 Volume above-mentioned, which only incidentally refers to it) is 

 a paper by Prof. Symington, published in 1891 (9). This author 

 also accepts the view which identifies the dumb-bell bone with 

 an element of the mammalian premaxilla. Both Turner and 

 Symington have recorded important details of the structure and 

 relations of this very interesting ossicle, and the results of their 



