11)10.] OSTIIACODA FROM TAXCIANYTKA. 749 



ill a coiioenti'ic' maimer. Inferior antenna' riitlier coarsely built, 

 with one of the terminal claws knife-sh:ij)eil and denticulated 

 along the inner edge (%. 3). The other Jimljs resenililing in 

 structure those in C>/pri<lopsi.s. 



Male of ahout same size ns feuiMle, and exliilnting a veiy 

 similar shape and sculptui'e of the sIk'II. 



Length of shell ()'6() mm., height O'^i^ mm., width U-;j9 mm. 



Remarks. — I cannot see any essential ditlerence between tlie 

 form described by Dr. Midler as the type of this genus, Z. mackc- 

 c/ascariensis, and the form recoixled by Dr. Vaviti, as Cypriclopsis 

 costata. Both these forms seem indeed to be identical, and as the 

 specific name proposed by Di-. Ydvra is the older one, it ought to 

 be retained for the pi'esent species. 



Occn.rrence. — Some few specimens of this form were found in a 

 sample from Victoria Nyanza (269), taken 25 4 '05 at Hukoba 

 (W. shore of lake). 



Disirihiitio}!. — Ugogo, East Africa [Vdrni), Mmlagascar 

 {MMler). 



24. ZoxocYPRis L/Evis, sp. 11. (Plate LXXII. figs. 4-7.) 



Specific CharacLers. — Female, Shell veiy tumid ; seen laterally 

 (fig. 4) of a somewhat trigonal shape, greatest height occui-riug 

 about in the middle and considerably exceeding half the length ; 

 anterior extremity somewhat obliquely rounded, postei'ior obliquel v 

 truncated below ; dorsal margin forming in the middle an abrupt, 

 almost angular curve, ventral margin rathei' deeply siimated in 

 the middle : seen dorsally (fig. 5) of regular ovifoi'm shape, 

 greatest width equalling two-thir> ' '' 'the length and occuriing 

 behind the middle, anterior extrcnlii^y much narrower than the 

 posterior. Valves rather thin and pellucid, neai-ly equal, and 

 clothed at each extremity with delicate liairs. Sui'face of shell 

 pel "ev.'ily smooth, without any trace of the concentric ridges found 

 in the preceding species. Muscular iuipi'essions in the centre of 

 each valve (fig. 6) densely crowded and somewhat diflei'ing in 

 form and arrangement from those in the two i^receding genera. 

 Inferior antennte of much t'he same structure as in Z. costata. oue 

 of the apical claws exhibiting a veiy similar knife-like shape and 

 coai'se denticulation of the inner edge (fig. 7). 



Length of shell 0-58 mm., height 0-33 mm., width 0-37 mm. 



Remarks. — The above-described form is umpiestionably con- 

 generic with the preceding species, agreeing with it in all 

 essential structural details. Yet it difi'ers very conspicuouslv in 

 even the character from which the pi-esent genus has been na.med 

 the surface of the shell being perfectly smooth, without the 

 slightest trace of any sculpturing. The generic name ])roposed 

 by Dr. ]\[iiller, of course, is somewhat inappropriate, since it does 

 not apply to all the speciev. 



Occarrence. — Some specimens nf this form, most of them not 

 in a good state of presei-vation, were found together with Z. castatu 

 in the above-mentioned samj)le from Victoria N^■all/.a. 



Proc. ZuoL. Soc— 191U, No. XLIX. " 49 



