112 CATALOGUE OF 



Vordertheil sehr verkiirzt, abgestutzt, gerundet ; Hiiitertlieil zu- 

 gespit/t gerundet. Wirbel sehr aufgeblasen und hervortretend. 

 Oberrand gewoblt, sehr scbmal, durch die schwach markirteu 

 Ecken des Schildes und Schildchens begrenzt. Vorderrand 

 kurz, steil abfallend. Unterrand sehr gebogen, ohne markirte 

 Grenze an die Nebenrander anschlicsseud. Hinterrand kurz, 

 steil abfallend, vvenig gewolbt. Liga-nent kurz, stark, Schloss 

 zusammengedriingt, kurz, zieinlich stark. Zahne wenig her- 

 vortretend. Perlmutter schwach weisslich ; Muskelnarbcri 

 kaum vertieft," 



When writing tlie above diagnosis the author momentarily 

 forgot that the external form of the Pisidium shell is the reverse 

 of that of other bivalves and it is therefore necessary to transpose 

 the two " Vorder- " and " Hinter-," which are italicized. The 

 lacking details concerning the hinge characters are : 



Hinge (PI. II, f. 8 ; IV, f. 2) about f the length of the shell, 

 wide, projecting well inwards, very strong, arcuate, with anterior 

 flexure. 



11. V. a. i. about f the length of the hinge-line, stout, very 

 strong, curving well inwards ; base strong and slightly 

 swollen; apex distal side of centre, prominent, bluntly 

 acuminate ; rid-yes rounded, distal almost vertical at 

 first, then nearly horizontal, umbonal fairly steep. 

 a. in. about ^ the length of a. /., narrow, strong, apposed to 

 the shell-margin ; apex at distal end, fairly prominent, 

 rectangular; ridges somewhat rounded, distal vertical, 

 umbonal sloping gradually. 



3. lamelliform, not very prominent, sharply flexed ; a 

 parallel to the shell-margin, b running diagonally 

 backward across the hinge-plate almost to its inner 

 margin. 



^>. /. about | the length of the hinge-line, rather narrow, 

 strong, curving with the shell-margin ; base strong ; 

 apex distal side of centre, distally directed, prominent, 

 obtusely acuminate; ridges somewhat rounded, umbonal 

 sloping fairly steeply, distal very steeply at first, then 

 nearly horizontal. 



p. in. about | the length of p.i., narrow, strong, straight, 

 erect, umbonally convergent to p. /. ; apex at distal 

 end, prominent, rectangular ; ridges somewhat rounded, 

 umbonal gradually sloping, distal vertical. 



L.V. n. about -| the length of the hinge-line, stout, strong, 

 faintly curving inwards ; base strong and swollen ; apex 

 central, somewhat distally directed, yery prominent, 



