BRANCHIURA FROM LAKE TANGANYIKA. 265 



mentioned, though these are faintly indicated in some cases. 

 The white spots are clearly visible. 



Occurrence. — Bukoba, 24/4/05. From surface of body, mouth, 

 and gill-chambers of a large Siluroid (? Bagrus degeni) — native 

 name, jYfui. Ten male and eleven female specimens. A 

 specimen of Argidus africanus was associated with these. 



Bukoba, 24/4/05. Associated with specimens of Argulus 

 africantds from surface of body and inside mouth of large Proto- 

 jytenis cethiopicus (length 1040 mm.). Three males and one 

 female. 



Bukoba, 24/4/05. From surface of body, mouth, and gill- 

 chamber of large Siluroid (? Glarias anguillaris) — native name, 

 Nshonzi. Two male and three female specimens. An indi- 

 vidual of Argulus africanus occurred with these. 



A single female specimen in the collection of the British 

 Museum has been more recently obtained from the lake. The 

 particulars recorded are : — " On skin of fish (' Male ') ? cattish. 

 Lake Victoria. Collected by G. D. H. Carpenter, 6. xi. 11." 

 This was associated with specimens of Argidus africanus. 



Nyasa. — I am indebted to my friend Capt. E. L. Rhoades, of 

 the British Naval Service on Lake Nyasa, for a small collection 

 of Argulidae from this lake. The specimens all proved to belong 

 to this species, and not to either of those obtained by Fiilleborn 

 in the lake. They are thus an addition to the number of forms 

 known in Nyasa, and at the same time a record of still wider 

 distiibution of the species. There are two male and four female 

 specimens, the only particulars given on the label being : — 

 " Fish-lice, ex. ^ Sungvja^ : Lake ISTyasa, 1908." 



River Nile. — In the British Museum collection are six male 

 and ten female specimens from yet another new locality. With 

 them was associated a single female specimen which I place, with 

 some hesitation, under Argidus africanus. They were obtained 

 by Mr. L. Loat, who gives the following details : — " Parasites 

 out of the mouth of a large ' Hala ' {Heterohranchus hidorsalis), 

 caught at the mouth of Lake No, White Nile, Jan. 30, 1901." 



Genus Argulus. 



All the remaining Argulids in the collection belong to the 

 genus Argulus itself. The number of species included in this 

 genus is fairly considerable, yet they are, on the whole, reason- 

 ably distinct, and there seems to be no grounds for subdividing 

 the genus. As the number grows, it becomes at the same time a 

 matter of increasing difficulty to diagnose a species accurately, 

 save at some length, since the differences are often of a minor 

 natui-e, concerning numerous parts of the external anatomy. 

 These facts render it more than ever difficult to offer to other 

 workers in this field a satisfactory key to the species. 



Wilson *, in 1903, made a serious attempt to provide a key to 



* Proc. U.S. Nat. Mus. vol. xxv. 1903, p. 701. 



Proc. Zool. Soc— 1913, No. XYIIL 18 



