SCHULTE, SEI WHALE. 473 



THE SKELETON. 

 (Plates LIV-LVII). 



SKULL. 



The cranium is broadly oval with a high arched vertex. The rostrum, though large, is far 

 from approaching its adult proportions, and the frontal and squamosal project as yet but moder- 

 ately from the sides of the brain-case. As a result of these several factors, together with the 

 decurvate tip of the rostrum and the caudal position of the temporo-maxillary articulation, 

 the skull has a strikingly avian appearance. The definitive elements in detail are well defined, 

 and, proportions aside, have the same general arrangements and connections as in the adult. 

 The most important exception to this statement is the all but complete exposure of the inter- 

 parietal, with the concomitant wide interval between the frontal and supra-occipital. There is 

 a broad fontanelle at the rostral margin and sides of the interparietal. On the base, the audi- 

 tory bullse are conspicuous for their relatively enormous size. 



The following calliper measurements are intended to afford some basis for estimating the 

 differential growth, by which eventually the skull attains its adult proportions: 



Table V. Measurements of skull of foetus of Balcenoptera borealis. 



mm. 



Length from tip of septal cartilage to condyle 100 . 



Breadth between rostral angles of orbital processes of frontals 48 . 



Breadth between caudal angles of orbital processes of frontals 61 . 



Breadth between rostral extremities of zygomatic processes of squamosals 61 . 



Breadth between extremities of postglenoid processes of squamosals 52 . 5 



Breadth between parietal eminences 42 . 5 



Breadth between extremities of exoccipitals 39 . 5 



Depth from rostral margin of supra-occipital to hamular process 47 . 



Length of rostrum 53 . 



Greatest breadth of rostrum 38 . 



Length of maxilla, from frontal border 48 . 



Breadth of same at orbital process 25 . 5 



Breadth of same at base of rostrum 21 . 



Length of premaxilla 55 . 5 



Greatest breadth of same, at middle of rostrum 5.5 



Length of nasal in median line 5.5 



Breadth of same at rostral end 3.5 



Distance from rostral end of nasal to rostral border of supra-occipital ". . 42 . 



Distance from rostral end of nasal to rostral border of interparietal 23 . 



Sagittal length of orbit 21 . 



Greatest dorso-ventral diameter of same 18. 



Depth from base to apex 



Length of hard palate 67 . 



Greatest length of palate bone ' 18 . 5 



Length of fibrous bulk 21 .5 



Breadth of fibrous bulla 16 . 



Length of hamular process 9-5 



In the description which follows I have concerned myself chiefly with the general archi- 

 tecture of the skull, omitting details regarding the individual elements, except in a few instances 



