Witson anp Martisx—TZhe Anatomy of the Muzzle of Ornithorhynchus. 189 
(15) Frower (and Gapow). “ Osteol. of Mammalia,” 3rd Edition, 1885, p. 243. 
(16) Symineron. ‘On the nose, the organ of Jacobson and the dumb-bell-shaped 
bone in the Ornzthorhynchus.” Proc. Zool. Soc. 1891, Pt. TV. p. 576. 
(17) Turner. Loc. cit. 
(18) Brugnt. “ Zootomie aller Thier-Klassen.” Lief. IV. Wien, 1875. 
(19) Parker, W. K. “The morphology of the Duck and the Auk tribes.” 
“Cunningham Memoirs,” No. VI. 1890, pp. 9 and 10. 
(20) Syminctoy. (Loe. cz¢.). 
(21) Parker, W. K. “The morphology of the Duck and the Auk tribes” (/oc. cz¢.). 
EXPLANATION OF PLATES. 
GENERAL REFERENCES THROUGHOUT FIGURES. 

n.c.—Nasal cavity. s.m.c. _—Superior marginal cartilage. 
s.m.—Septum nasi. epith. _—KEpithelium covering muzzle. 
a.n.—Alinasal. n.s.d. —Dorsal moiety of septum nasi. 
d.b.—Dumb-bell-shaped bone. n.8.v. —Ventral moiety of septum nasi. 
J, —Jacobson’s organ. pnp. —Prenasal plate of cartilage. 
h.p.—Horizontal partitions of fore part of nasal cavity. ant.nar.—Anterior nares. 
pz. —Premaxilla. sf. —Foramen of Stenson. 
n. —Nasal. p-nar. —Posterior nares. 
ma,—Maxilla. 8.M. —Socket for horny molar tooth. 
PLATES XXII.-XXIIl. 
Figs. 1 to 16.—Coronal sections of snout of Platypus. x 6 diameters. 
Fig. 17.—Ventral aspect of facial skeleton of Platypus. Cartilage tinted blue, bone yellow. Natural size. 
Note transverse dotted lines, showing planes of sections represented by figs. 4, 10 and 16. 
