SCHULTE. SEI WHALE. 413 



naris and the upper edge of the maxillary bone. As I could find no fasciculi of the supraorbital 

 muscle having this mesal course, and as there are such bundles in the next deeper layer, it would 

 seem possible that here they had failed to separate the superimposed muscles satisfactorily. 



The dorsum of the rostrum is covered by a muscle composed of fasciculi of transverse gen- 

 eral direction but converging towards the blow-holes. This muscle is situated immediately 

 below the blubber except at the base of the rostrum where it is overlapped for a short distance 

 by the frontalis and the laterally placed supraorbital muscle. It may be resolved into two 

 layers. The superficial one arises from the septal cartilage of the rostrum and the lateral margin 

 of the blow-hole. It is inserted into the whole length of the lip and at the tip of the rostrum 

 also by a few fasciculi into the extremity of the intermaxillary. The deeper layer has the same 

 general direction. It arises from the intermaxillary in its whole length and at its lateral margin 

 to a slight degree from the maxilla, except at the base of the rostrum where it gains a broad 

 origin from this bone, arising from the front of the sharp transverse ridge for more than half 

 its breadth laterad, and mesad extending to the elevation behind the nares in which the frontal 

 process of the maxilla ends. The fasciculi arising in this last situation would seem to corre- 

 spond in part to the retractores, in part to the compressores nasi of Carte and MacAlister. The 

 fasciculi arising most caudally from the maxillary ridge are directed sagitally, those from its 

 lateral portion mesad and rostrad ; they thus converge fan-like towards the rostral extremity 

 of the blow hole. From their direction it is clear that they dilate the nares, but the sagittal 

 fasciculi would seem farther to assist the superficial frontalis in elevating the orifice and turning 

 it caudad during respiration. The remainder of the layer inserts into the raphe its fasciculi 

 having a generally transverse direction but converging towards the nares. Megaptera shows a 

 close correspondence save that relatively its muscles are of smaller size. 



In addition to the foregoing three smaller muscles act upon each blow-hole. The larg- 

 est of these, the dilator naris of Carte and MacAlister's illustration arises from the premaxillary 

 close to the median line and in the proximal half of its prenarial extent, and from the adjacent 

 portion of the septal cartilage. It has a sagittal course and inserts into the rostral end and about 

 half the lateral wall of the narial passage, including the front of its sloping diverticulum. Its 

 main function must be to draw forward the blow-hole; dilation would seem to be abundantly 

 provided by the transverse rostral muscle. 



At the caudal extremity of the blow-hole is a small fan-shaped muscle superficial to the 

 frontalis. It arises from the fibrous tissue of the median line and inserts into the extremity of 

 the nostril and the adjacent portion of its median wall. 



The third muscle is placed below and parallel to the oblique lateral sinus of the nasal pas- 

 sage, from the wall of which it arises and also from the adjacent margin of the premaxillary. 

 It is directed dorsad and caudad and slightly mesad to the extremity of the blow-hole, where 

 it inserts by a short tendon, close to the preceding muscle. Its action would be to draw the 

 caudal end of the nostril ventrad and so perhaps assist in the elevation of its rostral extremity, 

 the obliquity of its pull being perhaps corrected by the small fan-shaped muscle mesal to the 

 blow hole. In Megaptera these three muscles have an identical arrangement. 



The collective action of the narial muscles must be considered in connection with the changes 

 in the blow holes during respiration. Their condition during this act is admirably shown in 

 Andrews's : photograph. Here the blow-hole has a subcircular contour and looks directly 



1 Plate XXX, Fig. 4. 



