740 



ARTHROPODA 



PHYLÜM VII 



Family 5. Oypridae Zenker. 



Minute, mostly reniform or elongate-ovate, corneous or corneo-calcareous shells, with 

 thin, somewhat unequal valves, one overlapping the other either ventrally or dorsally or 

 both. 



Recent Cypridae are chiefly fresh-water inhabitants, biit this is true in a lesser 

 degree of the fossil forras. All the Paleozoic representatives are marine, excepting 

 perhaps certain Carboniferoiis 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 granulöse and finely hirsute in dorsal region. Carboniferous. 



Cypris Müller (Fig. 1428). Shell reniform or oval, thin, translucent, smooth or 

 A hirsute, often punctate ; hinge edentulous, somewhat 



thickened ; ventral margin often sinuate. Tertiary to 

 Q Recent. 



Fio. 1428. 



Cypris faha Desm. Miocene; 

 Oeningen, Switzerland. A, Dorsal, and 



B, Lateral view. i5/j (after Bosquet). 



C, Valves composing fresh-water lime- 

 stone at Nördlingen. 



Fig. 1429. 



Cypridea rvaldensis 

 Sowb. Wealden ; Ober- 

 kirchen, Hanover. i5/j. 



Fig. 1430. 



Bo.irdia curla M'Coy. 

 Low er Carboniferous ; 

 Ireland. 15/, (after 

 Kirkby). 



Cypridea Bosq. (Fig. 1429). Like Cypris, but with a small hook-like projection 

 at the antero-ventral angle. Purbeck and Wealden. 



Bairdia M'Coy (Fig. 1430). Shell sub- triangulär 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 over- 

 lapping edge of left valve. Ordovician to Recent ; maxiraum in Carboniferous. 



Bythocypris Brady. Shell smooth, reniform, ovate or elliptical ; left valve over- 

 lappmg the smaller right valve usually on both dorsal and ventral margins. 

 lypically Recent, but a number of Paleozoic forms have also been assigned to this 

 genus. ° 



Macrocypris Brady. Similar to the last, but generally more elongate, posteriorly 

 more acuminate, and the right valve larger than the left. Ordovician and Silurian ; 

 also Jurassic to Recent. 



Pontocypris Sars. Like Bythocypris, except that the shell is very delicate, and 

 the hinge is simple without overlap. Silurian, Carboniferous, Pleistocene and Recent. 



Family 6. Cytherellidae Sars. 



Fio. 1481. 



Cytherdln mmpressa 

 (Münst.). Oligocene ; 

 Rflppelnionde, Belginm. 

 22/, (after Bosquet): 



_ Fmiily characters chiefly displayed by soft parts. Shell minute, 

 mequivalve, thick, calcareous, not notched anteriorly. 



Cytherella Jones (Fig. 1431). Shell oblong or sub-ovate, 

 compressed m front ; surface generally smooth, but sometimes 

 undulatmg and marked with pits and granules. Contact margin 

 Ol the larger right valve grooved for reception of fiange-like 

 edge ofsma 1er left valve. Ordovician to Recent. 



mr^If7 T^J^'T ^""^ ^"^^- ^il^ri^^- (?) Pachydomella 

 Ulrich (Flg. 1426, d) ■ Bosquetia Brady. Recent. 



