77 



This latter character, however, is only to be observed in fully grown specimens; 

 in the immature state of the animal, scarcely any trace of such a corner is seen, 

 the posterior extremity of the shell being quite evenly rounded off, as seen 

 from the figure given on the accompanying plate. Such young specimens 

 resemble closely in shape the form recorded by Brady in his Monograph under 

 the name of C. detecta (O. Fr. Miiller), which indeed may prove to be iden- 

 tical with the present species. 



Occurrence. I have taken this form rather abundantly in the 0stensj0 

 lake near Christiania at a depth of 2 or 3 fathoms on a muddy bottom. At 

 first only immature specimens were met with; but somewhat later in the summer 

 fully adult animals, with the characteristic produced posterior corner of the 

 shell, were captured, and such specimens were also found in another locality, 

 viz., in the Frogner dam located within the limits of the town. Only female 

 specimens of this species have as yet been observed. 



Distribution. Sweden (Aim), British Isles (Brady), Germany (G. W. Miiller), 

 Switzerland (Kaufmann). 



17. Candona Sarsi, Hartwig. 



(PI. XXXVI). 



Candona Sarsi, Hartwig, Zool. Anzeiger, Vol. XXII, 1899, p. 544. 

 Syn: Candona pubescens, G. O. Sars (not Koch). 

 dentata, G. W. Muller. 



Specific Characters. Female. Shell comparatively short and stout, seen 

 laterally, irregularly oval or somewhat subreniform in shape, with the greatest 

 height far behind and considerably exceeding half the length, dorsal margin, 

 nearly straight in the middle and somewhat ascending behind, then bent 

 downwards with a bold and quite even curve, ventral margin distinctly sinuated, 

 anterior extremity somewhat obliquely rounded, posterior much broader and 

 obtusely blunted, infero-posteal corner not at all exerted and broadly rounded 

 off; seen dorsally, oblong oval in outline, with the greatest width somewhat 

 exceeding Va of the length, anterior extremity more pointed than the posterior. 

 Surface of valves of a somewhat dull appearance, being densely granular and 

 all over clothed with unusually long and coarse hairs, giving this form a more 

 hirsute aspect than in most other species; hyaline borders in front and behind 

 very narrow. Both pairs of antennae much more slender than in C. caudata. 

 Posterior legs with the penultimate joint distinctly subdivided, the shortest of 

 the apical setae very small and hamiform curved. Caudal rami comparatively 

 short and stout, perfectly straight and somewhat tapering distally, apical claws 



