32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



to a small element not visible in adults but appearing in very young 

 skulls (like the one figured) as a thin cap overlying the upper portion 

 of the squamosal. Associated characters are: an enormously de- 

 veloped facial depression; a heavy jugal unlike that of any other 

 known toothed cetacean, and suggesting, in its robustness, the jugal 

 of the baleen whales ; a long rostrum much widened by building out 

 the sides beyond the level of the tooth row, and strikingly contrasted 

 with a narrow lower jaw with extremely long symphysis ; an unusually 

 large occipital condyle extending upward to involve the supraoccipital ; 

 palatine large, essentially normal in position, not forming any part 

 of the anterior wall of the slightly backward-sloping narial passage ; 

 pterygoid spreading forward over much of the palatine, but not ex- 

 tending laterally over the alisphenoid and not developing any secon- 

 dary plate ; maxillary teeth present in young only, their position nor- 

 mal with regard to the lower toothrow (not carried outward by the 

 widening of the rostrum as has been suggested) ; mandibular teeth 

 large, tusk-like in structure and in manner of growth ; hindermost ribs 

 supported by transverse processes which are perhaps not serially 

 homologous with those which support the others. 



The most advanced stage, so far as the upper portion of the skull is 

 concerned, is reached by Kogia (pi. 7, fig. 3). The parietal is now 

 obliterated as a separate element, even in skulls so young that the 

 bones of the cranium are readily disarticulated, and the summit of 

 the occipital has been carried forward to a level nearly over the 

 posterior border of the orbit. The median region of the frontal, 

 underneath the maxillary, has largely disappeared, so that a con- 

 siderable part of the anterior wall of the braincase is seen, on dis- 

 articulation of the skull, to be formed by the maxillary. In contrast 

 with PJiyscter the entire skull is shortened and the facial depression 

 is less extremely developed relatively to the occipital depth ; the 

 jugal is represented by its anterior extremity only, not distinguishable 

 from the lacrimal except in very young individuals ; the symphysis 

 mandibuli is short, and the form of the lower jaw as a whole presents 

 no contrast to the short, wide rostrum ; occipital condyle not unusually 

 large and not extending upward to involve the supraoccipital. The 

 structure of the palatine and pterygoid resembles that present in 

 Physcter; the narial passage slopes slightly backward ; the teeth are 

 tusk-like in structure and in manner of growth ; the hindermost ribs 

 are supported by transverse processes which may not be serially 

 homologous with those which support the others. 



The more important characters of the supergeneric groups of 

 modern toothed cetaceans are tabulated in the following key: 



