WATSON : ANATOMY OF HELICAEION. 105 



than does that of H. aloysii-sabaudicB (judging from Thiele's 

 figure), and this is also true of H. nyasanus, Smith ; but in both 

 these species the reproductive system lacks an amatorial organ as 

 well as the flagella. 



Several of the other species described by Thiele and Pilsbry, 

 such as H. bequaerti, Pilsbry, H. entagaricus, Pilsbry, H. insularis, 

 Thiele, H. kivuensis, Thiele, H. niger, Pilsbry, H. ruwenzoriensis , 

 Pilsbry, H. schubotzi, Thiele, H. suhsucculentiis, Pilsbry, and H. 

 succulentus, Mts., resemble H. crgptophalhcs in having an epiphallus 

 bearing two flagella ; but all these species, except H. schubotzi 

 and H. subsucculentus, differ from H. cryjJtophaUus in possessing 

 a dart-sac ; and in H. schubotzi neither the male organs nor the 

 shell-lobes seem to resemble those of H. cryptojohallus at all closely, 

 while H. subsucculentus cannot be very nearly related to that 

 species since it has a smooth protoconch. The descriptions of 

 Thiele and Pilsbry, however, are insufficient to enable one to judge 

 of the precise affinities of these species. 



In the various forms mentioned above the shell has reached 

 about the same stage of degeneration as in the two species described 

 in this paper. But there are several other forms occurring in 

 Tropical Africa in which the shell has become slightly more 

 degenerate, and the shell-lobes are a little broader and united with 

 each other over the front edge of the shell. Of these, H. semi- 

 membranaceus, Mts. — of which the reproductive organs and 

 radula have been figured by Thiele ^ — seems to have an epiphallus 

 with two flagella, like H. cryptophallus ; but it also possesses 

 a large dart-sac, and its radula is of a highly specialized type, 

 with an enormous number of narrow teeth, a specimen in the 

 British Museum which probably belongs to this species having 

 nearly 100,000 teeth, there being about 250 marginals on each side 

 in a transverse row. It is not surprising, therefore, that Pfeffer 

 placed this species in a distinct subgenus, Zonitarion} The form 

 from Abyssinia, for which Godwin-Austen established the sub- 

 genus Africarion, is evidently far removed from both H.gomesianus 

 and H. cryptophallus, as well as from H. semimembranaceus, for 

 it is portrayed as lacking not only a dart-sac and both flagella 

 but also a distinct epiphallus.* Nothing is known of the internal 

 anatomy of H. auriformis, Thiele, H. haliotides, Putzeys, //. 

 maculifer (Pilsbry), and H. putzeysi (Pilsbry), excepting some of 

 the characters of their reproductive organs.* These species bear 



» Deutsch. Zanlral-AJriha-Exped. {1907-08). vol. iii, 1912, p. 190, fig. xi ; 

 pi. vi, fig. 59. (Pilsbry is mistaken in saying that the genital organs of this 

 form have not been figured.) 



2 Jahrb. Deutsch. Malak. Gesell., vol. v, 1878, pp. 275-6 ; Abhandl. 

 Gebiete Naturwiss. Hamburg, vol. viii, pt. 2, 1883, pp. 4, 8, 9, 11. 



* Godwin-Austen, Mollusca of India, vol. i, 1883, pp. 154-6, pi. xlii. 



* Thiele, Deutsch. Zentral-Afrika-Exped, (1907-08), vol. iii, 1912, p. 198 ; 

 Pilsbry, Bull. Amer.Mus. Nat. Hist., vol. xl, 1919, pp. 259-64, figs. 122, 124, 127. 



