1881.] LAKES TANGANYIKA AND NYASSA, ETC. 295 



SO deeply umbilicated and less acutely carinated around the umbilicus. 

 The teeth, which frequently are present within the aperture of the 

 Egyptian species, do not exist in either of the Tanganyikan speci- 

 mens ; but the character of the rib bordering the peristome is similar 

 in both forms. 



43. LiMN^A NATALENsis, Krauss. 



Limncea natalensis, Krauss, Siidafrik. Moll. p. 85, pi. 5. f. 15 ; 

 Kiister, Con.-Cab. pi. 6. f. 1-3 ; Martens, Mai. Blat. 1866, pi. 3. 

 f. 8, 9. 



Hab. Lake Tanganyika (Hore ^ Thomson). 



Tliis species has a very extensive range, having been recorded from 

 Natal (Krauss), Abyssinia (Blan/ord and Martens), Lake Nyassa 

 (Kirk and Simons) ; and from the west side of the continent at 

 Benguela the same species, apparently, has been described under the 

 name of L. orophila. 



44. Physa, sp. 



Hab. liake Tanganyika (Thomson). 



This genus, not previously recorded from this locality, is repre- 

 sented by a single, probably young shell. It is very much of the 

 same character as P. nyassana, described in the Proc. Zool. Soc. 

 1877, p. 717, pi. 75. fig. 16-17. However, it is distinct; for ou 

 comparison with a specimen of that species of similar size, it proves 

 to consist of fewer whorls, has a less prominent spire, and narrower 

 umbilicus. 



45. Cyrena (Corbicula) radiata, Parreyss, var. ? 



Cyrena radiata. Parr., Philippi, Abbild. ii, p. 4, pi. i. f. 8 ; Cles- 

 shi. Conch. -Cab. (Corbicula) pi. 28. f. 16-18. 



Hab. Lake Tanganyika (Thomson). 



The shells from the lake are more finely and closely ribbed than 

 the specimens from the White Nile described by Philippi, and the 

 the hinge is a trifle stouter, but in all other respects agree very well. 



The shell figured by Sowerby in a wretched monograph in the 

 ' Conchologia Iconica,' under the name of " Cyrena radiata, Hanley, 



? MS." (pi. xi. f. 47 a, b), is quite distinct from this species ; 



but fig. 47c on pi. xiii. may be a bad representation of it. 



This species was recorded by me from Lake Nyassa (P. Z. S. 1877, 

 p. 718). On comparing the specimens from that locality with those 

 I'rom Tanganyika it becomes a matter of uncertainty whether they 

 should be regarded conspecific. The shells from the latter lake 

 are longer from the umbo to the ventral margin, and consequently 

 less transversely oblong ; their colour is a deeper violet within, whilst 

 the Nyassa specimens are fleshy-brown, varied by the external 

 umbonal and lateral violet rays. Such being the case, I prefer to 

 consider the shells before me as doubtfully belonging to this species, 

 until an opportunity occurs of studying this most difficult genus 

 more thoroughly. 



