158 Transactions of the Royal Society of South Africa. 



This species is founded on four examples, none of which are quite 

 mature, and it is obviously nearly related to C. mcbeanianus (Bnp.) which 

 it resembles in habit, being an underground, rather than arboreal species. 

 I have only been induced to accord it specific rank after consideration of 

 the evidence adduced by the anatomy, but there are also certain marked 

 points of difierence between the shells. C. mcbeanianus difiers from the 

 present species in that the whorls are considerably less tumid and less 

 rounded at the periphery, there being in young shells of junodi hardly a 

 vestige of carination, which is very marked in immature mcbeanianus, while 

 in the latter the umbilicus is a little narrower and considerably less open 

 than in the new species ; the roof of the mantle-cavity is ornamented with 

 dark and opaque white patches ; the recurrent ureter forms a closed duct 

 towards its anterior end, instead of being an open groove throughout its 

 length ; the jaw is more strongly folded, and there also seem to be some 

 slight differences in the radula. There can be no doubt therefore that 

 junodi is specifically distinct. 



Its general anatomy is of the same type as that of the other South 

 African species of Conulinus which have been dissected. Hitherto the 

 larger and broader species of this genus have usually been erroneously 

 placed in Pachnodus, but in their anatomy these species closely resemble 

 the smaller South African forms, whereas the type of the genus Pachnodus — 

 P. velutinus (Pfeifier) from the Seychelles — differs from them considerably 

 in its reproductive organs and still more in its radula.* This group of snails 

 from South and East Africa is also quite distinct anatomically from the 

 Palaearctic genus Ena (or Buliminus), in which many writers have placed it. 



Genus Rhachis Albers, 1850 (emend). 

 {=Rachisellus Bourguignat, 1889.) 



The necessity for dividing Rhachis into three distinct genera f on ana- 

 tomical grounds raises the determination of its genotype to so high a pitch 

 of importance that it may be well to recount, once again, the whole of the 

 facts concerning it, in hope of settling the question once for all. 



In the first edition of Die Heliceen, 1850, Albers proposed the subgenus 

 Rachis, with pallens Jonas as the first species, and included theTein ferussaci 

 Dkr., but did not nominate a genotype. 



In 1855 J Pfeiffer emended Albers' spelling to Rhachis, which appears 



* See Schacko, in Mobius : Beitr. z. Meeresfauna v. Mauritius u. d. Seychellen, 1880, 

 pp. 337-341, pi. xix, figs. 13-23 ; and Wiegmann : Mitt. Zool. Samml. Mus. Nat. Berlin, 

 vol. i, 1898, pp. 81-85, pi. iv, fig. 8. 



t See Thiele, Arch. f. Moll.-k. liii, 1921, pp. 149, 150. 



X Mai. Blatt. ii, p. 161. 



