1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 509 
the herbs and 'ow bushes. Dead shells are often met with in abundance 
in nat:ve fields. By far the most numerous in individuals are Limi- 
colariopsis, Limicolaria, and certain Homorus. No true Achatine were 
seen by the junior author anywhere on Mt. Ruwenzori. This is the more 
remarkable since at least one species of the genusis quite common in 
the lowland rain foresi of the neighboring Semliki Valley. 
The following is a list of the mollusks known from the zone of culti- 
vation (between 1,500 m. and 2,200 m.): 
Halolimnohelix hirsuta Ptychotrema edgarianum 
a mollitesta es sublimbatum 
_ Limicolariopsis ruwenzoriensis 7 silvaticum 
Limicolaria saturata Gulella linguifera 
Homorus lionepion = weblaa 
is fuscostrigatus “ camerant 
rR bequaerti ‘«  heteromphala 
‘s mambotensis Ht VEware 
a bicolor Thapsia curvatula 
Nothapalus sororcula Trochozonites leptalea 
re celatus debilis : Mesafricarion auriformis 
ferussactioides |  Helixarion ruwenzoriensis 
Subulina bequaerti -Kaliella barrakporensis 
= roccatit Atoxon brunneum 
Subuliniscus ruwenzoriensis Bukobia cockerella 
Curvella dautzenbergi Trichotoxon ruwenzoriense 
si conoidea . pardus 
Marconia lata ruwenzoriensis Cerastus retirugis 
Gonaxis cavallit 33 aloysii-sabaudix 
Varicostele subvaricosa Cyclophorus intermedius 
Ptychotrema geminatum nt elatior 
(2) The Mountain RAIN or CLoup Forest forms a girdle around the 
entire range, between the a'titudes of 2,200 m. (or 2,000 m.) and 2,800 m. 
It is a temperate and very humid zone containing many pecuilar types of 
trees (Dombeya, Sideroxylon, Pygeum, Allophylus abyssinicus (Hoch- 
stetter), Hagenia abyssinica J. F. Gmelin, ete.), shrubs (Bersama, Wethea, 
Mesa, Alangium, ete.), and lianas (Schefflera polysciadia Harms, etc.) 
that are entirely unknown in the rain forest of the upper Ituri and Sem- 
liki, but are represented as such or by closely allied species in the other 
East and Central African mountains. Epiphytes are abundant and there 
is a dense undergrowth of high, bushy, sublignose Acanthacex, Labiate, 
and Composite, while most of the lower herbs belong to genera of the 
northern temperate zone (Viola, Geranium, Sanicula, Plantago, Oro- 
banche, Alchemilla, Galium, Valeriana, Carex, etc.). Most of the land 
