1907.] CRUSTACEA OF THE THIRD TANGANYIKA EXPEDITION. 259 



the British Museum *. Among others are some which are stated 

 to have come from Nyasa and Tanganyika ; and since no notice of 

 these specimens appears to have been pubhshed, it seems desirable 

 to consider them, also, in the present paper. The following is 

 thus a complete list of the species at present known to occur in 

 the lakes in question : — 



Nyasa. 



Potavion {Potamonautes) inflatios (H. Milne-Edwards). 

 ,, {Potamonautes) orhitosjnnus^ sp. n. 

 ,, {Potamonautes) sp. ? 



Tanganyika. 



Potaraon {Potamonautes) platynotus^ sp. n. 



,, (Potamonautes) sp. ? 

 Platythelplnisa armata A. Milne-Edwards. 

 ,, maculata (Cunnington). 



,, conculcata, sp. n. 



2, Systematic N'otes and Prescription of New Species. 



Family Potamonid^(= Thelphusid m). 



Subfamily Potamonin^. 



Lake Nyasa. 

 Potamon (Potamonautes) inplatus (H. Milne-Edwards). 



Potamon {Potamonautes) inflatus Rathbun, Nouv. Arch. Mus. 

 Hist. Nat. Paris, 4*= ser., vii. (1905) p. 174 (ubi synon.). 



A single fair-sized male specimen in the collection of the 

 British Museum (Reg. No. 96.7.19.1) appears to belong to this 

 species. The only particulars given are : — " Kavisonda, Nyasa. 

 Presented by Dr. Ansorge." 



Potamon (Potamonautes) orbitospinus, sp. n. (Plate XVI. 

 fig- 1-) 



Description. — Carapace considerably flattened, antero-lateral 

 margins arcuated and denticulate, extending laterally less than an 

 orbit's breadth beyond the external orbital angle. No definite 

 epibranchial tooth, but the end of the post-frontai crest forming 

 a distinct corner at that point. Regions and sutures on carapace 

 moderately marked, latei-al regions exhibiting a series of small 

 slightly oblique granular ridges. Front rather deflexed, less than 

 one-third the width of the carapace, and with its anterior margin 



* By the courtesj' of the authorities of the Berlin Museum, co-tj'pes of some of 

 the species described by Hilgendorf from German East Africa were lent to the 

 British Museum for the purpose of comparison with those discussed here. I am 

 especially indebted to Dr. P. Pappenheim for detailed information regarding these 

 specimens. 



