184 Bulletin American Museum of Natural History [Vol. LIII 
This genus is strictly Ethiopian and Malagassan. On the African 
continent it appears to have much the same distribution as Pula, ex- 
tending northward to the delta of the Nile in the east, to Lake Chad and 
Senegal in the west; in South Africa it is found in Angola, Lake Ngami, 
the Zambezi Basin, Portuguese East Africa, and eastern Transvaal. 
The southernmost record appears to be Delagoa Bay. In the west the 
genus is unknown south of the Cunene. 
It is of considerable interest that a number of fossil species of Lanzstes 
have been found in the Tertiary of Lower Egypt. The oldest of these is 
Lanistes antiquus Blanckenhorn from the Middle Eocene or Lutetian of 
Faytm. It is regarded as an ancestor of the L. carinatus group. Lanistes 
bartonianus Blanckenhorn of the Upper Eocene (Bartonian) appears to 
be still more closely related to the recent L. carinatus (Olivier). The 
other species, Lanistes irreqgularis (Blanckenhorn) (=transiens Mayer- 
Eymar) and L. sandbergeri (Mayer-Eymar), appear to be much more 
depressed than any of the living forms. All four species, however, seem 
to belong to the subgenus Lanistes proper.’ 
While the shell of Lanistes is ordinarily spoken of as ‘‘sinistral,’’ 
it is well known to be really ultradextral or hyperstrophic; the unpaired 
organs of the soft parts, as first noticed by Troschel for L. ovwm,’ are not 
reversed, but occupy the same positions they have in dextral Ampullarii- 
dz. A planorboid ancestor of Lanzstes, similar to the American Ceratodes, 
is therefore to be sought in early Tertiary or Mesozoic deposits. Lanzstes 
irregularis and L. sandbergert appear to be transitional forms approach- 
ing this hypothetical ancestor. Ceratodes is disqualified as a group 
ancestral to Lanistes by being longisiphonate, a more evolved condition 
than the brevisiphonate Lanzstes. Since Lanistes had a planorboid 
ancestor, the openly coiled forms of the carinatus group, or Lanistes 
proper, are relatively primitive in structure of the shell, Meladomus 
being further evolved, and Leroya the final stage. 
The soft parts of Lanistes procerus langi are very similar externally 
to those of Pzla congoensis. Both epipodial lobes are somewhat larger 
(in the alcoholic examples). The orifice of the lung is close to the left 
border, 8 mm. long, placed substantially as figured for Pzla, the osphra- 
dium immediately anterior to it. The gill is on the right side, running 
back from the penis, as in Pila. The longitudinal ridge of the floor of 
the gill chamber is well developed, thin, and about 2 mm. high. The 
See C. Mayer-Eymar, 1901, Vierteljahrschr. Naturf. Ges. Ziirich, XLVI 22-34, Pl : 
M. Blanckenhorn, 1901, Centralbl. Mineral., Geol. u. Pala nt., Dp. ~27 3 Ne 1912 Proe, 
Ridtseol Goo Londed Sc occa ee. re) alaont., pp. 270-275. R. B. Newton, 1912, Proce. 
21845 Archiv f. Naturgesch., XI, 1, p. 2138. 
