230 MR. K, I. rOCOCK ON THE 



Fiinisciurus, the baculum is reduced to a small rod imbedded 

 near the apex of the distal portion, which is consequently 

 flexible. Tiiis portion, however, is specialised by the development 

 of a finely serrulated crest on each side, and is more sharply 

 marked off from the swollen portion of the glans, upon which it 

 is capable of being moved up and down. 



Finalh^ in HeUosciurus, the highest type, the distal portion is 

 developed into a flexible filiform process without baculum, the 

 thickened portion of the glans is longer and simpler, and the 

 preglandular portion of the penis is greatly lengthened. 



Returning to Protoxerus, it may be recalled that Thomas drew 

 attention to the likeness between its baculum and the baculum 

 of Baiufa. Unfortunately the penis of Ratiofa is unknown ; 

 but a similarit)^ may be traced between the glans of Protoxerus 

 and of Fanambulus if, as I suppose, the orifice opens in 

 Protoxerus on the swollen piart of the glans at the base of the 

 terminal slender portion. The chief differences in that case 

 between them will be reduction in the size of the baculum in 

 Protoxerus and specialisation of the glandular thickening from 

 which the slender terminal portion arises. In an}" case the like- 

 ness between the bacula and penes of Protoxerus and Funamhulus 

 is greater than the likeness between those same organs in 

 Funamhulus and Tamiodes. 



4, The African Ground-Squirrels. 



In the African Bristly Ground-Squirrels the glans penis is 

 relatively lai'ge, turns downwards at the apex, and has a well- 

 developed terminal baculum. 



In Euxerus erythropus the glans is long, and consists of two 

 parts, a subcylindrical proximal piece composed of soft, striate or 

 otherwise sculptured tissue, and a terminal smooth, compressed 

 piece with an elevated, convex upper edge which curves down- 

 wards distally to end in a rounded apex, behind which the 

 inferior border is concave. The upper edge ends posteriorly in a 

 twist ]iear the middle of the upper side of the glans. At the 

 distal end of the spong}^ portion beneath and a little to the right 

 of the middle line just behind the base of the compressed poi'tion, 

 the orifice opens. (Text-fig. 25, E-H.) 



The baculum, measuring 8-9 mm., conforms to the shape of 

 the distal portion of the glans, and consists of a stout, short 

 cylindrical proximal piece and a compressed blade, sometimes 

 rounded, sometimes hooked backwards at its inferior apex. The 

 upper side of the bone is slightly concave ; but carries a carti- 

 laginous crest, sometimes partialh* ossified, which runs backwards 

 some distance behind the proximal end of the bone and repre- 

 sents the distal dorsal crest of the glans. (Text-fig. 24, A-C.) 



The glans of Geosciurus capensis is tolerably similar, Avith a 

 similar dorsal crest ending in a twist proximally, but the distal 

 portion is not compressed, but gradually narrows to end in a 



