THE TANGANYIKA PROBLEM. 
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World forms, leaving only, in the section Thelphusime, those typical of the Old 
World, though occurring also in Australia. The principal points of resemblance to, 
and difference from, the members of this group, which this Tanganyikan crab 
presents, may be conveniently stated in tabular form. 
Points of resemblance to the Thelphusinte : — 
(1) . Presence of distinct post-frontal crest. 
(2) . Conditions of sutures on carapace. 
(3) . Form of external maxillipeds. 
(4) . Character of chelipeds. 
(5) . Spinuliferous condition of ambulatory dactyli. 
(6) . Normal seven-jointed nature of abdomen. 
Points of difference from the Thelphusinse : — 
(1) . Length of carapace more nearly equal to the breadth. 
(2) . Carapace considerably less vaulted. 
(3) . Antero-lateral margins relatively longer. 
(4) . Greater breadth and less deflection of front, with larger size of orbits and 
eyes. 
(5) . Second joint of antenna not distorted by deflexed front. 
(6) . Spotted nature of test. 
Two genera only — Parathelplmsa and Tlielphusa — are included by Ortmann under 
the heading Thelphusinse. Of these, Parathelplmsa was originally supposed to be 
typically Indo-Malayan in distribution, but in 1887 A. Milne-Edwards included 
under this heading several forms originally described as Tlielphusa from the African 
continent. The genus Thelplmsa is widely distributed over all parts of the Old 
World. Comparison with the large number of specimens belonging to these two 
genera in the collection of the British Museum showed that there are no forms 
which would seem to be closely allied to Limnothelphusa, but so far as general 
appearance goes, the specimens of Parathelphusa certainly agree most nearly. The 
latter have a carapace more elongated in proportion, have larger spine-bearing 
antero-lateral margins, and are considerably more flattened. The front, too, though 
deflexed, is less so than in Thelplmsa. On the other hand, however, in several of 
the described species the abdomen of the male is of the so-called “hour-glass” 
shape, while in all one spine only seems to be developed on the carpal joints of the 
chelipeds, and the second antennal joint is distorted in the common manner. The 
condition of the chelipeds is, however, in some species of Thelplmsa strictly com- 
parable with that of Limnothelphusa , so that in this respect we may consider the 
new form as occupying a somewhat intermediate position between these two old- 
established genera. 
Two other little-known genera, however, Hydrothelphusa and Platythelp/msa, must 
apparently also be included in the group, though they are not mentioned by Ortmann. 
Of these, the former, from the streams of Madagascar, was first described in 1872 
by A. Milne-Edwards. The description, however, was very brief, and though he 
has since given a further account, as well as a- figure of the dorsal aspect, our 
information is still unfortunately very incomplete. The front here, instead of being 
deflexed, is said to be almost horizontal, while the carapace is onsiderably flattened 
