562 MAMMALIAN PRENASAL CARTILAGE. 



Monotreme type on the one hand and that of the Bat on the other, 

 while by contrasting figures 7, 4, 5 and 6 the nature of the Bat 

 and Marsupial developments becomes manifest. 



My best thanks are due to Mr. A. G. Hamilton for the specimen 

 of bandicoot examined, and to Prof. Wilson and Mr. J. J. Fletcher 

 for other kind assistance. 



EXPLANATION OF FIGURES. 

 Plate XLIY. 



Reference Letters. 



a.ii,, anterior nares — relative position indicated by dotted lines; a.n.s., 

 anterior portion of nasal septum; c, supposed remnant of caruncle; Fr.^ 

 frontal; i.n.p., internasal passage; J.c, Jacobson's cartilage; J.o., Jacob- 

 son's organ; Mx., maxillary; Na., nasal; n.f.c, nasal- floor cartilage; n.p.c.^ 

 naso-palatine canal; n.s., nasal septum; p.c, papillary cartilage; Pmx.^ 

 premaxillary; p.n., prenasal cartilage; p.n'., prenasal at its anterior part; 

 'p.Pmx., palatine process of the premaxillary; P.Vo., prevomer; S.c.^ 

 Stenson's cartilage; Vo.., vomer; ?'.s., vascular spaces; *, supposed apical 

 point of primitive beak in Platypus; f, a small detached piece of cartilage 

 of doubtful signification. 

 Fig. 1. --Longitudinal median section of the snout of On^^7Aor%?^c•^»s { x 5). 



Fig. 2. — Longitudinal median section of the snout of Echidna ( x 5). 



Fig. 3. — Longitudinal median section of head of 4-in. mammary foetus of 



common Phalanger ( Trichosuriis vulpecula) ( x 4). 

 Fig. 4. — Transverse vertical section of portion of nose of Australian Bat 



(Miniopteriis schreihersii, Natt.) in the region of the outlet of 



Jacobson's organ ( x 45). 

 Fig. 5. — Transverse vertical section of portion of nose of Australian Bat 



(Miniopterus schreihersii, Natt. ) near the front of Stenson's duct 



(x 45). 

 Fig. 6. — Transverse vertical section of portion of nose of the Bandicoot 



( Peramehs nasutaj in region of the anterior part of Jacobson's 



organ ( x 12). 

 Fig. 7. — Transverse vertical section of portion of nose of 6-in. feetal calf 



(X 6). 



