148 ON THE "dumb-bell-shaped" BONE IN OKNITHORHYNCHUS, 



(9) Symington, J. " On the Nose, the Organ of Jacobson, and 

 the dumb-bell-shaped Bone in the Ornitlhorhynchus," P.Z.S. 

 1891, p. 575. 



(10) Parker, W. K. " On the Structure and Development of 



the Skull in the Common Snake ( Tropidonotus natrix),^' 

 Phih Trans. Roy. Soc. Lond. 1878. 



(11) Howes, G. B. "On the probable Existence of a Jacobson's 



Organ among the Crocodilia ; with Observations upon the 

 Skeleton of that Organ in the Mammalia, &c.," P.Z.S. 

 1891, p. 148. 



(12) Parker, W. K. "On the Structure and Development of 



the Skull in the Mammalia," Part ii., EdPMtata ; Part iii., 

 Insectivora, Phil. Trans. Roy. Soc. Lond. 1885. 

 (1.3) Herzfeld, p. " Ueber das Jacobson 'sche Organ des Mens- 

 chen und der Saugetiere," Zoologische Jahrbiicher, Bd. iii. 

 (Anat. u. Entwickelungsgesch.), p. 551 (1889). 



(14) Balogh, C. "Das Jacobson'sche Organ des Schafes," Sit- 



zungsber. K.K. Akad. Wien, 1862. 



(15) Parker, W. K. "The Morphology of the Duck and the 



Auk Tribes," 'Cunningham' Memoirs, No. vi. 1890. 

 For a bibliography relating to Jacobson's organ and its rela- 

 tions up to ^ 889, Beard's paper in Zoolog. Jahrbiicher, Bd. iii. 

 p. 762, may be consulted. Additional papers are cited in Parker's 

 memoir above quoted (12), p. 6. 



EXPLANATION OF FIGURES. 

 Plate viii. 



Fig. 1. — View of dumb-bell-shaped bone of Ornithorhynchus from below, 

 showing palatine plate and vomerine spur, enlarged four dia- 

 meters. 



Fig. 2. — View of dumb-bell-shaped bone from the left side ( x 4). 



Fig. 3. — View of dumb-bell-shaped bone from the left and above ( x 4). 



Fig. 4. — Sagittal section of anterior part of snout of adult Ornithorhynchus, 

 parallel with and to the right of the mesial plane. The section 



