700 MB. W. A. CtJNNINGXOSr ON A NEW [May 16, 



foreign growths is easily accounted for. It is, I understand, the 

 largest individual that Mr. Moore has ever seen, and from its soft 

 texture it had clearly recently undergone ecdysis, becoming for 

 the time free from encrusting organisms. 



Affinities. — That this Crab finds its nearest allies among the 

 freshwater group of the Thelphusida3 there can, I think, be little 

 doubt. Of the three sections into which Ortmaun has subdivided 

 the group ^, the Pseudothelphusinae and the Trichodactjdinse may 

 be at once dismissed, as differing most markedly in the character 

 of their external maxillipeds. This excludes the New World 

 forms, leaving only, in the section Thelphusinse, 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 Thelphusinse ■ : — 



(1) Presence of distinct post-frontal crest. 



(2) Conditions of sutures on carapace. 



(3) Form of external maxilhpeds. 



(4) Character of chelipeds. 



(5) Spinuliferous condition of ambulatory dactyli. 



(6) Normal seven-jointed natui-e 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 — Parathelphusa and Thelplmsa — are included 

 by Ortmann under the heading Thelphusiute. Of these, Para- 

 thelphusa 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 Thelphusa from the 

 African continent. The genus Thelphttsa is widely distributed 

 over all ])art3 of the Old World. By the kindness of Prof. Jeffrey 

 Bell, M.A., I have been permitted to examine the large number 

 of specimens belonging to these two genera in the collection of 

 the British Museum. Among them there are no foi'ms which 

 would seem to be closely allied to Limnothclphusa, but so far as 

 general appearance goes the specimens of Parathelphusa certainly 

 agree most nearly. The latter have a carapace more elongated in 



1 Zool. Jahrb. (Abth. f. Syst.) Bd. vii. 1894, p. 487. 



- The term ia here used as instituted bj' Ortmaun, though in his scheme ol 

 classification he does not refer to the genera Hydrothelphicsa and Fluty- 

 thelphusa. ^ Ann. Sci. Eat. vii., Zool. t. 4. 



