STRINGOCEPHA LID. 313 
Animal with sigmoid arms, destitute of spiral terminations ; 
cirri in pairs. 
Krausstna, Davidson, 1859. 
Syn.—Kraussia, Davidson, not Dana, 1852. 
Distr.—6 sp. South Africa, Sydney, New Zealand ; low-water 
to 120 fathoms. K. rubra, Pallas (exxxv, 53, 54). 
Shell transversely oblong; hinge-line nearly straight; beak 
truncated, laterally keeled; area flat; foramen large, deltidium 
rudimentary ; ; dorsal valve longitudinally impressed, furnished 
inside with a forked process rising nearly centrally from the 
septum; interior often strongly tuberculated. The apophyses 
are sometimes a little branched. 
Animal with rather small oral arms, the spiral lobe very 
diminutive. 
ArGIore, Eudes Deslongchamps, 1842. 
Etym.—Argiope,a nymph. Syn.—Megathyris, d’Orb., 1847. 
Distr.—5 sp. North Britain, Madeira, Canaries, Mediterra- 
nean; 30-105 fathoms. Fossil, 19 sp. Oolite—;. Europe. A. 
decollata, Chemn. (cxxxvi, 60- 63). 
Shell minute, transversely oblong or semiovate, smooth or 
with corresponding ribs; hinge-line wide and straight, with a 
narrow area to each valve; foramen large, deltidium rudimen- 
tary; interior of dorsal valve with one or more prominent, 
submarginal septa; loop two- or four-lobed, adhering to the 
septa, and more or less confluent with the valve. 
Animal with oral arms folded into two or four lobes, united 
by membrane, forming a brachial disk fringed with long cirri; 
mantle extending to the margins of the valves, closely adherent. 
CISTELLA, Gray, 1853. (Zellania, Moore, 1855.) Shell minute 
orthiform ; texture fibrous; hinge-area short, foramen angular, 
encroaching on both valves; interior of dorsal valve as in The- 
cidium, witha single central septum and broad margin. Recent, 
Tsp. Fossil, 3 sp. Lias—Great Oolite; Britain. A. David- 
soni, Moore (cxxxvi, 64, 65). 
Famity STRINGOCEPHALIDA. 
Shell suborbicular, the hinge-margin rounded; the under valve 
with a deltidium and opening under the prominent beak; cardinal 
process very large, almost touching the opposite valve; loop. 
attached to the crura by their neural edges. 
SrrincocepHAus, Defrance, 1824. 
Etym.—Strinxg (stringos), an owl; cephale, the head. 
Distr.—S. Burtini, Defrance (cxxxvi, 55, 56, 66,67). 2 sp. 
Silurian, Devonian; Europe. 
Shell punctate ; suborbicular, with a prominent beak; ventral 
21 
