PROCEEDINGS OF THE NATIONAL MUSEUM. ^l. 57. 



into an additional segment it will require a younger stage of the skull 

 to establish the fact beyond question. 



As it is not the object of the present study to go into the question 

 of the relationship of Rhynchocyon and its allies, I shaU omit a descrip- 

 tion of the base of the skull, teeth, etc. The lower jaw, however, 

 displays several features which come within the scope of the present 

 study, and I here call attention to them. The back part of the jaw 

 has a very characteristic and peculiar appearance, which is not at all 

 usual in the Mammalia. This is seen in the eversion or outward twist 

 of its angular portion, the long backward slope of the ascending 

 portion of the ramus, the very small coronoid, and the unusually 

 high position of the condyle. The condyle has its greatest develop- 

 ment in a transverse direction and is convex from before backwards. 

 That which is of the greatest interest, however, is what appears to be 

 an indistinct suture, separating the articular surface or head of the 

 condyle from the rest of the bone, as if it were an epiphysis. This 

 suture, if it is really the remains of one, foUows the limits of the 

 articular surface closely in front, but is not so evident behind. In a 

 like manner, upon the inner surface of the jaw situated just below the 

 opening of the inferior dental canal is a small sunken tubercle or bony 

 knob, well marked off by a distinct fissure, resembling the remains of 

 a suture and connected behind by a distinct groove, which extends 

 backwards to the edge of the jaw just below the angle. This groove 

 when examined carefully has the appearance of being the remains of a 

 suture, but this may be deceptive. It may be said of both of these 

 peculiarities of the jaw that they are symmetrical or exactly alike in 

 the opposite halves. 



Cercoctenus and other Macroscelididae. — The first of these genera 

 is represented by some 32 skulls of all ages, of the species Cercoctenus 

 sultana. In this species the lachrymal has a small though dis- 

 tinct preorbital extension with the opening of the lachrymal canal 

 within the orbital cavity. On the rim of the orbit it is produced into 

 an unusually prominent crista orhitalis, which is greatly augmented 

 by the addition of two flattened plate-like ossicles, articulating by 

 their applied edges, with its superior and outer border. The upper 

 of these ossicles, which is the smaller of the two, lies at the junc- 

 tion of the lachrymal with the frontal, and the lower or larger, 

 articulates with the lachrymal and m.alar near the point where these 

 two bones join. 



The lachrjrmal has the usual form and relations in this group of 

 Insectivores, articulating above with the frontal, in front with the 

 maxillary, on the rim of the orbit with the malar, and within the eye 

 cavity with the palatine, maxillary, and frontal. The presence of 

 these ossicles here described, together with the prominent crista to 

 which they are attached loosely by suture, give a characteristic 



