640 MB. E. A. SMITH 0?f LATTD A>T) FRESHWATEB [Nov. 7 



with, nodules, but much smaller than the sutural series. It is a 

 remarkable-looking shell, and probably peculiar to the lake. 



26. Phtsa nyasana, Smith. 



Hab. Karonga, west shore but towards the northern end of 

 Lake Nyasa (R. Crawsliay). 



The original specimens (described P. Z. S, 1877, p. 717, pi. Ixxv. 

 figs. 16, 17) were obtained at the southern part of the lake. 



27. Physa kabongensis. (Plate LIX. fig. 15.) 



Testa ovcita, angusta, perforata, pallide fuscescens ; anfractus 3|, 

 celeriter crescentes, coiivewi, infra suturam plus minus disiincte 

 marginati, lineis incrementi sculpii, idtinyvs ohlique descendens ; 

 spira brevis, ohtvsa ; apertura angusta, elongoia, longit. totius 5 

 patdo svpera7is ; columella contorta, rejle.va ; labrvm tenue, 

 intus leviter incrassaium. 

 Longit. 7f onillim., diam. 54 ; apertura 5| longa, 2| lata. 

 Hah. Karonga. 



This species is narroM'er than P. nyasana, has the spire more 

 elevated, the last whorl obliquely descending and the aperture 

 consequently shorter. This is the third species now knoMn from 

 Nyasa. 



28. PlajS'oebis (Plaxorbula) alexandbina, var. 

 Hab. Karonga, Lake Nyasa. 



This is the first recoi'd of the genus from the lake. The single 

 specimen is a link between those from Tanganyika (figured by me 

 P. Z. S. 1881, pi. xxxiv. figs. 30-30 b) and the typical form from 

 Egypt. M. Bourguignat (Ann. Sci. JN'at. Zool. vol. x. 1890, p. 23) 

 has considered this variety a distinct species under the name of 

 Planorhida tanganiJcana. 



29. Unio xyassaexsis, Lea. (Plate LIX. figs. 16, 17.) 

 Hab. Angoni-Land, south end of lake Xyasa (A. Wliyte). 



This species is very variable in form and sculpture and offers a 

 fine field for the manufacture of so-called species. Lea described 

 three forms of it under as many names, and M. Bourguignat ' has 

 given a name to a variety A^hich was figured by me in the Society's 

 Proceedings, 1881, pi. xxxiv. fig. 34. 



30. Unio (Metapteba) joiu^stoni. (Plate LIX. figs. 18-20.) 

 Testa compressa, transversa, elongata, antice nasuta, postice 



acuminata, ad marginem dorsalem stirsum acute alata, tenuis, 

 'pallida, epidermide dilute virescente postice obsctire radiata 

 induta, versus umbones margaritacea, inceqinvalvis, valde 

 inaquilateralis, utrinque angustissime Mans ; valvce striis 

 incrementi tenuibus sculjttce, sujira umbones tenuiter connigatce ; 

 margo dorsi incurvati(S, ventralis late excurvatus, posticus inter 

 alam dorsalem et extremitateni posteriorem valde sinuatus ; pagina 



1 Bull. Soc. malacol. France, 1889, vol. vi. p. 38. 



