264 Mr. R. C. Wroughton on 



Cuspidaria approximata, Smith. 



Cusjiidaria approximata, Smith, Aun. & ^fag. Nat. Hist. 1890, 

 vol. xviii. p. 373 ; Illust. Zool. ' Investigator,' Moll. pi. viii. 

 figs. 2-2 a. 



Hub. Station 322, Andaman Islands, 378 fath. 



A single specimen 2 mm. longer than the type. Specimens 

 from the Gulf of Oman have been presented to the British 

 Museum by Mr. J. C. Melvill. 



XXXVIT. — Notes on the Genus Otomys." 

 By R. C. Wroughton. 



The material available to me for examination in the collec- 

 tion of the Natural History Museum amounts to about 

 150 specimens (skins and skulls) from some 30 localities. 

 Though Africa north o£ the Equator is very poorly repre- 

 sented, yet, at first sight, the total material seems sufficient 

 for a fairly exhaustive classification ; but, on careful com- 

 parison, I am convinced that this is not so, and that the area 

 south of the Zambesi, which is especially well represented by 

 series from many different localities, is just that in which 

 the results I have obtained are the furthest from finality. 



All but two species of the genus have the anteiior molar 

 in the lower jaw composed of four laminre or their equiva- 

 lents. Setting aside for the moment these two aberrant forms 

 as Section III., the genus may be easily further divided into 

 two sections, according as the lower incisors are smooth (or 

 but faintly grooved), or are markedly grooved ; and each of 

 these Sections falls again naturally into two groups. lu 

 Section I., comprising the forms with smooth lower incisors, 

 those in which the posterior molar in the upper jaw is 

 composed of four laminse (or their equivalents) and large 

 bullae form the Brantsi group, and those in which m^ is 

 composed of five laminai and the bullae are quite small form 

 the unisulcatus group. In Section II., comprising the forms 

 with grooved lower incisors, those with a single groove as in 

 irrorutns, Brants, are readily separated from those with a 

 double groove as in Jacksoni, Thos. 



The geographical distribution fairly closely agrees Avith 

 these main divisions of the genus. Thus Section I. is found 

 in a strip of country running across S. Africa between 28^ 

 and 32° S. hit. Of Section II. the Jacksoni group is found 



