110 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Genus Helicarion, Fer.^ 

 Subgenus Zonitarion, Pfeffer. 



Protoconcli smooth, without spiral sculpture ; remaining 

 whorls usually with microscopical spiral striae, excepting in some 

 of the species with large shell-lobes. Left shell-lobe narrow or 

 triangular, becoming flattened out into a low straight fold in those 

 forms in which the shell-lobes are united. Right shell-lobe 

 variable in size, often with a median ridge when large. Median 

 projection of jaw low or obsolete. Central and lateral teeth rather 

 narrow, with, anteriorly prolonged bases ; marginals extremely 

 numerous (in H. semimemhranaceus, at least). Epiphallus bearing 

 two flagella, the distal one sometimes of a considerable size. 

 Spermatheca usually somewhat elongated. Genital atrium 

 bearing a muscular dart-sac. 



Known distribution : Equatorial Africa, from the borders of 

 Uganda to the west coast. 



Section Angustivestis, Pilsbry. 

 Last whorl of shell spirally sulcate. Shell-lobes narrow and 

 separate. 



ruwenzoriensis, Pilsbry, 

 Jcivuensis, Thiele. 

 niger, Pilsbry (type of section). 

 bequaerti, Pilsbry. 



Section Entagaricus, Pilsbry. 

 Shell-lobes separate, the right broadly rounded, the left triangular. 

 Dart-sac mushroom-shaped. 



entagaricus, Pilsbry, 



Section Belonarion, Pilsbry. 



Shell-lobes concrescent, the right broad, the left triangular. An 

 excitatory organ ( = dart-sac ?) is included in the penial sheath, 

 which reaches the retractor muscle. 

 putzeysi (Pilsbry). 



Section Zonitarion, s.s. 

 Shell-lobes concrescent, the right broadly rounded with a median 

 ridge, the left reduced to a low straight fold. A penial sheath 

 apparently extends to the retractor muscle. 

 haliotides, Putzeys. 

 semimemhranaceus, v. Marts, (type). 



1 On pp. 19 and 20 (or 23 and 24) of Ferussac's Tabl. Syst. Anim. Moll, 

 Fam. des Limaqons, 1821, this word is misspelt Helixarion ; but on p. 67 

 (or 71) of the same work Ferussac himself corrected this blunder, and it would 

 geem to be a pity to ignore his correction, as Pilsbry has done, 



