212 ^ MR. R. I. POCOCK ON THE 



to South Brazil are closely i-elated to Sciurus. (3) The subfamily 

 ISTannosciurinse must be abolished as composed of heterogeneous 

 elements, alike only in convergent characters*. 



In 1923 (Proc. Zool. Soc. 1922, pp. 1171-1212) I published a 

 paper on the external characters of all the species of Sciuridte 

 available to me as fresh or spirit-preserved specimens. But for 

 want of adequate material I was compelled to omit consideration of 

 the penis and baculum. To Mr. Thomas's kindness in lending me 

 the collection of bacula prepared under his orders at the Natural 

 History Museum, I now owe the opportunity to figure and 

 describe, not only the specimens of this bone described in general 

 terms in his paper, but also those of a few Petauristidae, of 

 Citellus, Xerus, and some others which he intended, granted time, 

 to work out himself. To the account of the.se bacula I have added 

 descriptions of the penis and bacula of such specimens of Sciuridfe 

 as I had preserved for the Zoological Society's collection. 



Description of the Penis and Baculum. 

 1. The Palcearctic and American Species. 



In Sciurus vidgaris the apex of the penis is compressed and 

 upturned where the terminal blade of the baculum runs into it. 

 The orifice opens on the right side behind and below the tip, aiad 

 is surmounted by a small fleshy lappet ; and the small pi-ocess of 

 the blade of the baculum forms a marginal projection just below 

 and in front of the orifice. The soft swollen tissue enveloping the 

 apes of the penis is continued backwards as a curved crest from 

 above the orifice to terminate near the middle of the dorsal 

 surface of the glans ; and laterally and inferiorly it is defined by 

 a groove from the wrinkled, more slender, and rod-like proximal 

 portion of the glans. My observations on this species agree with 

 those of Tullberg, who figured the penis and the extracted 

 baculum from two points of view. (Text-figs. 18, A ; 19, A, B.) 



I find, moreover, that the glans penis of Sciurus {Neosciurus) 

 carolinensis is of precisely similar structure. Thomas also 

 described the baculum of *S'. vulgaris, and pointed out that the 

 type of baculum found in that species occurs also in a number of 

 other forms from Asia and North and South America. In the 

 collection of the British Museum the bacula of the following- 

 species demonstrate this truth: — S. vulgaris from Europe, persicus 

 from Asia Minor, lis from- Japan, niger from ISTorth America, 

 carolinensis from Tennessee and England (imported), nayoritensis 

 from Jalisco in Mexico, langsdorffi from the Sierra de Ohapada, 

 ingravii from Eio Janeiro, and variabilis from South America. 

 And there is no reason to doubt that the glans penis in all these 

 species conforms to the shape of the baculum. In view of these 



* True at all events of the African 3Iyosciurus and the Oriental Nannosciuriis, 

 which respectivelj' fall into line with other species of the regions thej* inhabit. But 

 the baculum of the South American genus has yet to be examined. 



