646 ARTHROPODA SUB-KINGDOM VII 
perhaps certain Carboniferous species. Fossil remains are extraordinarily profuse in 
certain deposits, and the family is an important rock-builder. 
Palaeocypris, Brongt. Shell 0°5 mm. long, sub-ovate, smaller posteriorly than in 
front ; surface granulose and finely hirsute in dorsal region. Carboniferous. 
Cypris, Miller (Fig. 1346). Shell reniform or oval, thin, translucent, smooth or 
hirsute, often punctate; hinge edentulous, somewhat 
thickened ; ventral margin often sinuate. Tertiary to 








Recent. 
C Cypridea, Bosq. (Fig. 1347). Like Cypris, but with 
eee ah 
LEG 
Fic. 1346. 
Cypris faba, Desm. Miocene; Fic. 1347 Fic. 1348. 
Oeningen, Switzerland. A, Side, and . o Bairdia curta, M‘Coy. 
B, Dorsal view. 15/; (after Bosquet). Cypridea Waldensis, Carboniferous Limestone ; 
C, Valves composing fresh-water Sowb. Wealden; Ober- Ireland. 15/; (after 
limestone at Nordlingen. kirchen, Hanover. 15/;. Kirkby). 
small hook-like projection at the antero-ventral angle. Purbeck and Wealden. 
Bairdia, M‘Coy (Fig. 1348). Shell sub-triangular or rhomboidal, with the 
greatest height near the middle, generally smooth, both extremities narrowly rounded 
or pointed. Dorsal margin more or less strongly convex; hinge formed by overlap- 
ping edge of left valve. Ordovician to Recent ; maximum in Carboniferous. 
Bythocypris, Brady. Shell smooth, reniform, ovate or elliptical; left valve over- 
lapping the smaller right valve usually on both dorsal and ventral margins. Typically 
Recent, but a number of Palaeozoic forms have also been assigned to this genus. 
Macrocypris, Brady. Similar to the last, but generally more elongate, posteriorly 
more acuminate, and right valve larger than the left. Ordovician and Silurian ; 
Jurassic to Recent. 
Pontocypris, Sars. Like Bythocypris, except that shell is very delicate, and hinge 
simple without overlap. Silurian, Carboniferous, Pleistocene, and Recent. 
Family 6. Cytherellidae. Sars. 
Family characters chiefly zoological. Shell minute, inequivalve, thick, caleareous, not 
notched anteriorly. 
Cytherella, Jones (Fig. 1349). Shell oblong or sub-ovate, compressed in front ; 
surface generally smooth, but sometimes undulating and marked 
with pits and granules. Contact margin of the larger right valve 
grooved for reception of flange-like edge of smaller left valve. 
Ordovician to Recent. 
Cytherellina, Jones and Holl. Silurian.  ? Pachydomella, 
Ulrich. Devonian. Bosquetia, Brady. Recent. 

Family 7. Entomidae. Fia. 1349. 
Cytherella compressa, 
Shells relatively short, strongly convex, reniform, ovate or rounded eek Bi : ips 
° 5 Z . uppelmonc elgium. 
quadrate, sub-equivalve, with a more or less well-marked depression near 2), (after Bosquet). 
the middle of dorsal region. Surface sculpture concentric or radiate. 
Entomis, Jones (Figs. 1350, 1351). Shell sub-ovate or fabiform; valves with a 
slightly curved sub-median vertical furrow extending to hinge line; in front of furrow 
occasionally a rounded tubercle. Surface marked generally with raised, concentric, 
ee 
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