590 Bulletin American Museum of Natural History [Vol. LIII | 
*Chytra kirk *Randabelia catoxia 
*Paramelania bridouxt x a hamyana 
$ a e var. jouberts *Hirthia littorina 
“4 crassigranulata Mel, SO OOSE 
é cs damont *Hdgaria arenarum 
3 iridescens Bi IEG 5 ORBSAUCOTTS 
e . minor Beh es 
*Joubertia baizeana Bit deena ptotes 
pre se spinulosa sete iS var. obliqua 
erecta, stanleyana By Soe Ose 
*Lavigeria callista cates ‘< var. nassatiformis 
aon ala combsa ei pe@aeucostae 
i oe coronata eal eee var. callopleuros 
phe diademata oy Whey a OUIOIUAD 
epee: grandis Pe Is SULA US 
eae jouberts eS ane LEC 
BY Ras pereximia * “  ygriabilis  * 
aeteta ns ruellaniana *Lechaptoisia ponsonby 
: 
The 70 thalassoid forms belong to 20 genera.! We provisionally re- 
gard Syrnolops'sanil Anceya as forming a peculiar family Syrnolopside, 
of doubtful affinity since the soft parts and operculum are unknown; 
possibly related to Amnicolidee. As more fully explained in the taxonomic 
part of this work, the other thalassoid genera are in our opinion true 
Melaniide. We include in that family even the genera Tiphobia and 
Bathanalia, which many authors have separated into a distinct family 
Tiphobiidee. 
The thalassoid gastropods of Tanganyika live under at least three 
different sets of environmental conditions. Most species of Paramelania, 
Edgaria, Reymondia, Tanganyicia, and Spekia are shore snails that live 
firmly attached to rocks where they are fully exposed to the movement 
of the waves. Of Hdgaria nassa J. E. 8. Moore says: ‘“ During life this 
molluse inhabits the surface rocks of Tanganyika, and its shells are 
always richly encrusted with the green algee which clothe the rocks for a 
considerable depth. It is sluggish, and appears to browse within a very 
limited area, like the Patellas of the ocean beach.’’? On p. 246 of Moore’s 
book we also read: ‘‘Upon the shore rocks and flourishing among the 
surf and the breakers of Lake Tanganyika there are several species of 
small molluscs, which in the fauna of the lake fill the place of the Littor- 
nas and Neritinas of the sea shores, and among these littoral forms 
there occurs in great abundance the animal, to the empty shell of which 
‘We rank Burtonilla as a subgenus to Anceya, Coulboisia and Giraudia as subgenera to Baizea, and 
Bythoceras as a subgenus to Paramelania. 
21903, ‘The Tanganyika Problem,’ p. 250. 
