1927] Pulsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 433 
with a golden gleam in some lights to tawny olive; the posterior ridge is usually 
darker green, and the rest of the shell is indistinctly marked with narrow, faint, 
greenish rays. The interior is highly iridescent, pale bluish lavender, blue toward the 
borders, and with an irregular light vinaceous drab stain in the beak cavity and its 
neighborhood, and often some darker bronzed markings. The anterior adductor scar 
is lightly impressed, the other muscle scars not impressed. The visceral muscle scars 
are well in the beak cavities, oblong, oblique and single in each valve. There is an 
extremely narrow, rounded ridge running the length of the hinge, which under the lens 
is seen to be slightly swollen a little behind the beaks, forming an extremely weak, 
vestigial pseudocardinal tooth in each valve. 
Length, 96.0 mm.; height, 31 mm.; diameter, 20 mm. 
Length, 90.5 mm.; height at beaks, 28 mm.; at posterior third, 30 mm.; dia- 
meter, 18 mm. 
While this species is related to M. rostrata, it differs by the shape of 
the posterior end and wing, and the less wrinkled surface. - Mutela 
zgyptiaca (Pallary), from the Canal of Mahmudieh, Lower Egypt, 
appears to be very closely related to M.lang:. According to Pallary’s 
measurements of five specimens, it is higher relative to the length, the 
height 35.5 to 38 per cent of the length in xgyptzaca, including its two 
varieties, 30.9 to 32.3 per cent in langi. We would consider this without. 
significance were it not that the habitat of lang: is remote from that of 
egyptiaca. Possibly both represent one widely spread species, which 
generally has not been differentiated from M. rostrata. 
Mutela mabilli (A. T. de Rochebrune) 
Plate XLI, Figure 1 
Mutelina mabilli A. T. pe RocHEBRUNE, 1886, Bull. Soc. Malacol. France, ITI, p. 7. 
Mutelina mabillei A. T. de Rochebrune. GrRmMain, 1908, in A. Chevalier, 
‘L’ Afrique Centrale Frangaise,’ p. 569. 
Mutela mabillti A. T. de Rochebrune. Simpson, 1900, Proc. U.S. Nat. Mus., 
XXII, p. 906; 1914, ‘Descript. Cat. of Naiades,’ p. 1360. 
Mutelina paludicola A. T. DE RocHEBRUNE, 1886, Bull. Soc. Malacol. France, 
ii, pe 
Gancini or Nganchu, on the right bank of the Congo River (type locality of both 
mabilli and paludicola; Thollon Coll.). 
Medje (Lang and Chapin Coll.). 
A single example from Medje agrees well with the account of this 
unfigured species except that it is not solid, being about as thin as M. 
rostrata. . The color is blackish, shading into very dark green upward, and 
having some brownish concentric streaks. The beaks are at the anterior 
fifth of the length. The concentric wrinkles are much more pronounced 
than in M. rostrata. 
Length, 90 mm.; height at beaks, 23 mm.; at posterior third, 33 mm.; diameter, 
16 mm. 
