328 EUG. DADAY DE DEÉS 
« Carapace-valves obovate, resembling in form the shell of 
a Pisidium. Anterior extremity somewhat broader than poste- 
rior, much more convex and gaping. Beaks prominently ele- 
vated, and situated near the 
anterior extremity. The shell is 
of a light vellowish horny colour 
internally and externally, and 
of a fine glossy polished appea- 
rance and finaly pellucid. The 
ribs are numerous, about 27 im 
number, elevated, and smooth. 
| | | The spaces between are sligthly 
Fig. 79. — Cyzicus politus (Baird) ; 
(Sec M Baird}. = a conchala dla |CONCAVE, Land Are beau 
ere ; 6, conchae supra Visee; Cpaté . Motted with numerous mal 
valvulae concharum. : 
impressed punctations. 
Hab. India. Capitain Boys. Brit. Mus. » 
Par la forme de ses valves le Cyzicus politus (Baird) rap- 
pelle plusieurs espèces : les Cyzicus dubiosus Dad., interme- 
dius Dad., melitensis (Baird), Lofti (Baird) et brasiliensis 
(Baird), mais il diffère de toutes par la structure de la 
surface des valves. Sous ce rapport le Cyzicus politus (Baird) 
peut être rapproché du Gyzicus californicus (Pack). Il est 
impossible de décider si Gyzicus politus (Baird) est une espèce 
propre où un simple synonyme de l’une des espèces citées plus 
haut, sansune nouvelle description plus détaillée. 
? Cyzicus Caldwelli (Baird). 
Fig. 80, a-c. 
Estheria Caldwelli Baird W., 12, 13, p. 148, Tab. 15, fig. 4, a-b; Grube E., 52, 
p. 233. 
« Carapace-valves swollen, ovate, of a pale horn-colour. Um- 
bones large, prominent, and ferruginous-coloured, placed at 
about one-third distance from the anterior extremity. Dorsal 
margin short, and nearly straight. Anteriorextremity rounded, 
short, a little broader than posterior extremity, which is long 
and rounded. Ventral margin rounded. Ribs of carapace nume- 
rous, rather narrow. Interstices roughlv and strongly punctate. 
