135^ MUTELA 



]\lL'Tei,A iJOUKGUiGNATi P>ourguignat. 



Shell somewhat elonsiated. irregularly rhomboid, rather sol- 

 id, convex, inequilateral ; beaks low ; posterior ridge full, 

 rounded, ending in a rounded point at the base of the shell ; 

 above the ridge there is a wide, shallow, radial impression ; 

 dorsal line straight : anterior end rounded, much cut away be- 

 low ; base curved, full in the middle; posterior end obliquely 

 truncate ; surface regularly, concentrically striate, lightly shin- 

 ing, olive, obscurely, linearly rayed ; hinge with- faint teeth in 

 front ; nacre rich orange with whitish border, iridescent. 

 A'alves widely gaping at anterior base and behind. 



I.ength 53, height 21, diam. 12 mm. 



Lake Nyanza. 

 Mutela bourguignati Roukcuicnat, Esp. Ouk., 1885, p. 8. — 



Simpson, Syn.. 1900, p. 904. 



Decidedly long rhomboid, w'ith the base somewhat produced 

 medially. Bourguignat describes the nacre as splendidly iri- 

 descent, orange with a ^^•hite border. Credited to Ancey in litf. 



Yar. smithi von Martens. 



"Proportionately higher and shorter, the height being to 

 the length as i .2 2.25 ; the upper posterior angle is stronger, 

 being about 140" : ventral margin very convex in the middle. 

 Beaks situated at from 2-7 to 1-3 of the length. 



Length 75-86, height of beaks 30-33, of wnng 32.5-35, diam. 

 20-24. distance from the beaks to the end of the hinge 35-41 

 mm." (von Martens). 



Type locality. Lake A^ictoria-Nyanza. 

 Mutela bourguignati E. A. Smith, Ann. Mag. Nat. Hist., (6), 



X, 1892, p. 128, pi. 12, fig. 16. 

 Mutela bourguignati smithi von Martens, Besch., 1897, p. 



255. — Germain, Arch. Zool. Exp. et Gen., (5), I, 1909, p. 



\^ar. triincata von Martens. 



"Posterior end ver\- short, more rapidly ascending below and 

 steeper above; upper posterior angle being about 130°. Height 

 to length as i :2.33. A'''entral margin only slightly curved. 



