1893.] SHELLS FROM BRITISH CE^'TEAL APEICA. 641 



interna pulcTierrime marf/arifacea, iridescens, interdum j'xdlide 

 rosacea; dens cardinalis anticus valvce sinistrce clongatus, leviter 

 corrvrfatus, v. dextrce duplex, dens postims tmiciis v. dextroi 

 elonr/atns, rectus, tenuis, proyninens, v. sinistrce duplex. 

 Lom/it. 53 rnillim., alt. 30, diam. 9i. 

 Hab. Lake Mweru (li. Crawshaji). 



The shells here described are probably only small representatives 

 of this species. The species is quite unlike any other known form 

 from Africa. It recalls the Unio d.elpliinvs, Gruner, from Malacca, 

 on account of the dorsal \ving, and agrees with it also exactly in the 

 hinge-dentition and the ligament. In form it even more closely 

 resembles H>/ria elongata, Swainson, from British Guiana (Exotic 

 Conch, p. 29, pi. xxiv.). 



31. Pliodon spekei (Woodward). 



ffab. Sumbu, S.E. Tanganpka (E. CrawsJiai/). 



Only one species of this genus from Lake Tanganyika has come 

 under the writer's observation, although as many as twenty-six 

 so-called species are enumerated by Bourguignat \ 



Like many of the '■'■species^' from the Central African lakes 

 described by that author, they are of little or no value. 



32. MuTELA (Spatha) 2fTASSAEXSis, Lea. 



Hah. Nyasa {A. WJiyte). 



The specimens in the present collection are considei'ably larger 

 than Lea's type, being 3| inches long, 2\ high, and 1| in diameter. 

 Besides being more oval than ^S'. ruhens, as pointed out by Lea, 

 this species is more inaequilateral, the beaks being situated much 

 more anteriorly and less prominent. The impression of the 

 ^-isceral-sac attachment near the anterior adductor scar is smaller 

 also. 



EXPLANATION OF PLATE LIX. 



Fig. 1. Eniiea johistoni, p. 633. 



2. karongana, p. 033. 



:}, 4. Helix (Pe//a) wln/iei, p. 034. 



r», 6. Virijjarufi mweniensis, p. 630. 



7. , var. paf/odifonnis, p. 030. 



S. crawshayi, p. 637. 



9. Cleopatra johiistoni, p. 637. 



KJ. viwerucnsis, p. 637. 



1 1 . Melanm woodwardi, p. 038. 



\'l. mweniensis, p. 63V^. 



13. imfatrix, p. 630. 



14. cravwhayi, p. 030. 



1.5. I'lii/sa h-aroiigennis, p. 040. 



16, 17. Unio 711/assaensis, p. 040. 

 IS, 10, 20. johnstoni, p. Mi). 



' Nouvcautes Malacol., I. Unionicla- et TridinidjE du lac Tanganika, 1880, 

 pp. 66 0.3 : loonofrr. Malaool.Taiipnnika. 18fiS, pis. xxxi. xxw. 



