52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



posterior orifice to the infraorbital canal, and by the situation of the 

 orbits at a level decidedly in front of that of the narial passages. The 

 orifice of the antorbital canal, as in Delphinapterus, lies distinctly 

 behind the level of the anterior border of the orbit, a peculiar position 

 as compared with ordinary mammals which would appear to show 

 that special readjustment of the parts has taken place, either through 

 a backward movement of the base of the rostrum which has carried 

 the foramen with it, or by a secondary forward movement of the 

 orbit after conditions had been established resembling those seen in 

 the Delphinina'. On the other hand the posterior basal portion of the 

 pterygoid of Monodon does not spread laterally over the surface of 

 the alisphenoid in the peculiar manner seen in Delphinapterus and 

 Stenodclphis. The relations of these two bones are of the ordinary 

 dolphin type (No. 23,455, U. S. National Museum) except that there 

 appears to be more of a tendency for the anterior basal portion of 

 the pterygoid to expand outward in the direction of the optic canal. 

 The anterior reduplication of the pterygoid is narrow and ridge-Hke, 

 suggesting the conditions which occur in the ziphiids and in Delphin- 

 apterus, but of a somewhat intermediate character. This combina- 

 tion of peculiarities taken in connection with a form of dental speciali- 

 zation which is unique among known cetacea appears to be sufficient 

 to place the genus Monodon in a subfamily of its own. 



Ziphiidce. — The beaked whales have recently been regarded as 

 near relatives of the sperm whales, often as members of the same 

 family, chiefly because of similarities in the tusk-like manner of 

 growth of the teeth and in the relationship of the hindermost ribs 

 to the vertebrae. These characters now appear to be of little 

 weight relatively to the type of skull-telescoping and the structure 

 of the palatine and pterygoid. In these very important morphological 

 features the beaked whales dififer completely from the sperm whales 

 and essentially agree with the delphinids. Telescoping is strictly of 

 the delphinine type (see pi. 5, fig. 5, and pi. 7, fig. 4), the maxillary 

 passing back horizontally over the eye even in such an excessively 

 modified skull as that of Hyperoodon. Pterygoid greatly enlarged, 

 covering almost the entire surface of the alisphenoid, its inner and 

 outer reduplications present but low and ridge-like. Posterior orifice 

 of infraorbital canal formed by maxillary, palatine, pterygoid and 

 lacrimal, though the maxillary and pterygoid may be excluded 

 (especially in the genus Berardiu's'). It seems proper to consider 

 the beaked whales as near relatives of the delphinids, though suf- 

 ficiently characterized by the peculiarities of the skull, dentition and 



