578 PROCEEDINGS OF THE NA TIO.\ . 1 1. M I 'SE UM. 



t PSEUDOSPATHA LIVINGSTONENSIS Bourguignat. 



* Spatha tanganyicensis SMITH (part), Proc. Zool. Soe. Lond., 1880, pi. xxxi, tig. 8a; 



1881, p. 296, pi. xxxiv, tig. 32. 



* Burtonia lirinyatonensia BOURGUIGNAT, Moll. Fluv. Nyan/.., 1883. p. 20. 



* Burtonia elongata BOURGUIGNAT, Un. and Ir. Tan., 1886, p. 34; Icon. Mai. Tan., 



1888, pi. xxv, fig. 3. 



* Burtonia contorta BOURGUIGNAT, Un. arid Ir. Tan., 1886, p. 39; Icon. Mai. Tan., 



1888, pi. xxvi, figs. 3-5. 



Lake Tanganyika. 



PSEUDOSPATHA SUBTRIANGULARIS Bourguignat. 



* Jiurtonia subtriangularis BOURGUIGNAT, Un. and Ir. Tan., 1886, p. 35; Icon. Mai. 



Tan., 1888, pi. xxv, fig. 2. 



* Burtonia yrandidieriana BOURGUIGNAT, Un. and Ir. Tan., 1886, p. 42; Icon. Mai. 



Tan., 1888, pi. xxvn, figs. 1-3. 



Lake Tanganyika. 



PSEUDOSPATHA BOURGUIGNATI Bourguignat.' 



* Burtonia bourguignati BOURGUIGNAT, Un. and Ir. Tan., 1886, p. 38; Icon. Mai. 



Tan.. 1888, pi. xxvn, figs. 4-5. 



Lake Tanganyika. 



The following species are uii figured and unknown to me. 



* Burtonia jouberti BOURGUIGNAT, Uu. ;md Ir. Tan., 1886, p. 40. 



* Burtonia bridouxi, BOURGUIGNAT, Un. and Ir. Tan., 1886, p. 40. 



All from Lake Tanganyika. 



Genus HYRIOPSIS Conrad, 18S3. 

 (Type, I'nio delphinus Gruner.-') 



Hyriopsis CONRAD. Pr. Ac. N. Sci. Phila., 1853, p. 269. 



Shell large, compressed, rhomboid-elliptical, dorsally winged and gen- 

 erally biangulate behind, sometimes produced in the post-basal region; 

 beaks low, mostly compressed, the sculpture consisting of numerous 

 concentric ridges nearly parallel with the growth lines, generally 

 extending well on to the disk of the shell, the earlier ones fine, often 

 slightly nodulous or doubly looped; epidermis olive to brown, some- 

 times faintly rayed; pseudocardinals two or three in the left valve, one 

 to three in the right, when young com pressed, but often breaking into 

 irregular denticles when old; laterals long, compressed, two in the left 

 valve and one in the right, sometimes vertically striate, the left valve 

 often having a sort of raised lamellar tooth at or .just behind the beak. 



1 Said to be of Joubert in the literature. 



2 The general make-np of the shells of this genus, Cyclomya, and Cristaria seems to 

 indicate close relationship to each other, and a not distant one to the submenus 

 I'roptcra of Lampsilix, and 1 should not l>r surprised to learn that the marsupinni 

 occupies the posterior part of the outer gills in distinctly marked ovisacs. 



