liRAZZ.l'A I 37 I 



Genus ERAZZ.^,A Bourgiiignat, 1885. 



Brazzcra Boi'kcuignat, Esp. Ouk., 1885, p. 32. 



Shell thin, transparent, brilliant wine-colored, elliptical, 

 greatly inflated, with a slight post-dorsal wing, and a high, 

 double posterior ridge ; beaks smooth, compressed, but the 

 region below them full ; hinge edentulous, filiform, with two 

 ligaments, one internal, the other external ; there are three- 

 groups of muscular impressions and several dorsal scars nm- 

 ning in a row from the beak forward and downward ; upper 

 border of the left valve projecting over that of the right, 

 forming a sinuous wing. 



Animal unknown. 



Type, Bracccra anceyi Bourguignat. 



A set of Naiades inhabiting Lake Tanganyika of rather light 

 structure, generally inflated, with edentulous hinges. The 

 upper border of the left valve is said to project over that of 

 the right. The texture of the shells is generally a rich violet 

 or wine color, within and without. I cannot help feeling im- 

 pressed when I look at the figures of the Naiades of Lake Tan- 

 ganyika that from some cause many of them are more or less 

 diseased and that the shells in such cases are somewhat dis- 

 torted or abnormal. And 1 am inclined to believe that Bour- 

 guignat and other authors of the new school have selected 

 these diseased, distorted shells and made of them types of 

 species. 



This appears to be a valid genus, belonging to the MitteHdcc. 

 I copy for . the most part Bourguignat's description, which 

 leaves out some essential characters. I have never seen any 

 of the species. 



Key to sPEcins o^ Brazz.t:a. 



Ilmbonal region much elevated and inflated. 



Shell long, rhomboid elliptical, wider than high. 



bourguignati. 



Shell short, height greater than the width zfentrosa. 



TJmbonal region but little inflated. 



Shell obovate. short. coulhoisi. 



Shell long elliptical. elongata. 



Ilmbonal region not elevated. ance"^:!. 



