544 Bulletin American Museum of Natural History [Vol. LIII 
africana (probably subspecies globosa), Pzla sp. (ovata?) Lunistes procerus 
langi, and Bulimus kisalensis. Of these, Lanistes procerus langi is by far 
the most common and most striking on account of its large size; it is 
the preferred food of the open-bill stork, Anastomus lamelligerus Tem- 
minck, which is extremely abundant in this region, often living in colonies 
(see p. 537). Many of the swamp mollusks are during the rainy season 
carried by the rising waters much beyond the limits of pools and marshes, 
into the flood plain. With the coming of the dry season they congregate 
in the pools that fill the depressions, but these, too, finally evaporate and 
the whole plain becomes for five or six months one expanse of baked clay 
or sand, fully exposed to the glaring rays of the tropical sun. Under such 
conditions most of the snails left stranded in the pools undoubtedly die; 
but certain species appear to be able to stand this prolonged desiccation 
without injury. This is especially the case with Lanistes and Pula. 
Writing of the common Lanistes of Angola (perhaps wrongly referred to 
L. ovum), Morelet says: ‘‘Mr. Welwitsch gives us, concerning this species, 
an observation which proves that life may remain latent for a consider- 
able length of time in the Ampullariide. When the lakes dry up during 
winter, or when the ponds are drained through irrigation, these gastro- 
pods bury themselves deep in the soil. One day our traveler picked up 
on the shore of one of these reservoirs, lumps of hardened mud which 
had been dug up and which contained several specimens of L. ovum. They 
were forgotten at Loanda in a dark room of his house and it was only 
two years later that he thought of soaking them in order to extract the 
animal they contained. But, much to his surprise, he saw several of them 
return to life, leave the bowl in which they had been placed and crawl 
over the sides. Moreover, this persisting vitality is not the privilege of 
the Ampullariide alone nor even of certain gastropods. Strange to say, 
some acephalous mollusks possess it to a similar degree, as shown by 
Rang’s curious observation of Anodonta chacziana published by him in the 
Annales du Museum (1834, IV, p. 309).’! In the alluvial plain of the 
upper Lualaba live specimens of Lanzstes procerus, tightly closed with 
the operculum, may often be found laying on the ground during the dry 
season. The Bulinus, Planorbis, and Lymnee, however, do not appear to 
withstand drought to the same extent. Many of them die before they are 
rescued by the first rains; in some cases they may escape by hiding deep 
down in the mud.” 
11868, “Voy. Welwitsch, Moll. Terr. et Fluv.,’ - 95. - 
2Planorbis spirorbis, in Kurope, is known sometimes to form a sort of epiph i i 
, , 1s ; piphragm against evaporation 
and perhaps some of the Central African species do likewise. ati 8 
