DE. J. MUBIE ON THE OEGANIZATION OF THE CAAING WHALE. 247 



an upper lateral, alar, and rudiment of sesamoid are there. Quite within the narial 

 passages on each side of the cavity, partially below but vertical with the alar cartilage, 

 is a small globular bag which opens by a fissure into the nares. This sac, which I have 

 named the maxillary sinus, is fibrous, smooth, yet glandular within, and contained 

 sebaceous or ceruminous-like substance. Still higher on each side, and lying between 

 the maxillary, tiu-binal, and lachrymal bones, and therefore nearer the nasals, is another 

 semilunar depression or shallow sinus 5 inch long, nearly vertical, though somewhat 

 crescentic. A thu-d and much better marked cavity exists on the floor of either moiety 

 of the nares. This, a slipper-shaped fossa or sinus-like fold, is sunk forwards, or pro- 

 duces a well defined step about an inch long betwixt the deeper postnarial chamber and 

 the more raised floor of the anterior segment of the interior nares. The two last- 

 mentioned pairs of fossa are each smooth-surfaced and lined by a continuation of the 

 moist mucous membrane. Anteriorly the nares are capacious, and under control of the 

 flabby but muscular parietes. 



Secondly, as regards the Tapir, the late Mr. H. N. Turner' has shown, and a dissection 

 on my own part" verifies, that quite within the nose, in the semicircular notches outside 

 the projecting nasal bones, are two long, smooth-lined sacs or naso-frontal maxillary 

 sinuses. Each of these is somewhat /"-shaped, the blind and bulbous posterior extremity 

 being curved inwards, the anterior straighter end freely communicating with the interior 

 nares. These elongate sinuses are mainly hollowed out of what Tmner supposes to be 

 the lateral nasal cartilages, continuous with the septal. He thinks alar cartilages are 

 absent ; in this I do not quite agree. The muscles of the proboscis are arranged after 

 the usual type of the nasal group, with a special pair of long levators. 



I refer the reader to my illustrations and account of the anterior cranial muscles of 

 Lagenorhynchus albirostris and Grampus rissoanus, and the figures 63 to 67 of the 

 present plates, in lieu of redescription. The latter has one layer less than the former, 

 and the diminutive fasicles connected with the naso-facial can^l are not so markedly 

 differentiated. 



As regards the action of the different layers in Globiceps &c., they are nearly identical 

 in the several forms. The superior layer is a dilator of the blow-hole and compressor of 

 the maxillary sac ; the second sheet assists the first. The third set of fibres assimilates 

 to the preceding in its use ; but there is an additional mechanism of the parts induced 

 by its upper anterior tendinous slip. This runs quite into the nasal blubber ; and the 

 fibres cross well over, so that, while creating tension of the fatty nodosity, a certain 

 amount of backward pressure follows, and aid is lent to the elastic fibrous cushion which 

 usually keeps the commissure of the nasal orifice closed. The small, short, and semi- 

 circular muscle connected with the posterior canal acts as a retractor and compressor to 

 it. What I have termed premaxillary or naso-labialis, while less fleshy in G. melas 



' P. Z. S. 1850, p. 103. 



' RhinocJioerus sumatranus, Journ. of Anat. & Phys. vol. vi. p. 138, and figs. 8 & 9, pi. x. 



