1 



54 * 



S- rostellum n s. p. 24, T. Ili, f. 3. Small, slightly longer than 

 broad, broadly ovai, constriclion shallow, opening wide; semicell 

 flatly ovai, spiny, ^pines small, the one next the constriction rather 

 larger and directed downwards, more prominent at one angle owing 

 to a pecLiliar twist in the semi-cell giving it a considerable resem- 

 blance to a bird's beak, a number of small spines (about 14) are 

 arranged round the margin of the semi-cell and 2 to 3 rows within 

 the margin ; end view quadrangular, with sides concave, spiny, and 

 angles a little produced, one more prominent on account of the twist. 

 Membr. smooth: isthmus broad. Dim. 3i-33 « 29-31 « 13-14 v.. 



Xanthidìuiii qiiadricornuium n. s. p. 27, T. IV, f 5. Medium sized, 

 a little longer than broad, constriction deep, opening widely; semi- 

 cells elliptical, slightly reniform at the base, with two spines about 

 the middle of each side; the centre of the semicell thickened, den- 

 sely, and irregularly scrobiculate ; end view elliptical, slightly c^ua- 

 drangular, with a spine at each angle, sides thickened. Isthmus 

 narro wed. Membr. smooth. Dim. 47, 5-5o « 45-47,5 « 14-15 u.. 



Arihrodesmus longicoriiis n. s. p 28, T. Ili, f i. Like A. Incus, 

 but differs in the very long, nearly parallel, or slightly diverging spi- 

 nes and (in front view) triangular semi-cells. Dim. 26 « (with sp.) 

 76 « 8 u. 



Cosmariuni alpestre n. s. p. 29, T. I, f. 6. (C. rotundatum R. et B. 

 mss.). Large, rounded oblong, a little longer than broad, constriction 

 very slight; semi-cells smoothly rounded, from a very broad isthmus; 

 side view circular, from a broad base: end view very broadly ovai; 

 membr. closely and fìnely punctate; isthm. very broad, with a row 

 of rather larger punctae on each side. Dim. 90-105 « 75-90*79 a.; 

 thickn. 60 a. 



Sehr wenig verschieden von C. connatum Bréb. und Disphin- 

 ctium ellipticum Delp. 



C. Archerà n s. p. 3o, T. I, f. 5. Species large, somewhat irre- 

 gularly ovai, truncate, about a fourth part longer than broad; semi- 

 cells from slightly reniform base, with dose constriction, opening 

 out widely into the broadly rounded sides, ^vhich converge upwards, 

 gradually becoming slightly undulated to the sharply and somewhat 

 irregularly dro\ui-out truncate ends: side view circular, with a nar- 

 rower rounded part upwards; end view smoothly ovai. Constriction 

 deep, dose. Isthmus moderate. Membr. finely punctate. Dim. 107- 

 1 12 « 80-87 '^ 32-35 [j.; truncate end, 33 y..; length of drawn-out end, 

 10 a. 



