STRINGOCEPHALID^. 313 



Animal with sigmoid arms, destitute of spiral terminations ; 

 cirri in pairs. 



Kraussina, Davidson, 1859. 



Si/n. — Kraussia, Davidson, not Dana, 1852. 



Dint?: — 6 sp. Soutli Africa, Sydney, New Zealand ; low-water 

 to 120 fathoms. K. ruhra^ Pallas (cxxxv, 53, 54). 



Shell transverse!}^ 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 nearlj^ 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. 



Argiope, Eudes Deslongchamps, 1842. 



Etym. — Argiope^ a nymph. Syn. — Megathyris, d'Orb., 184T. 



Distr. — 5 sp. North Britain, Madeira, Canaries, Mediterra- 

 nean ; 30-105 fathoms. Fossil, 19 sp. Oolite — ; Europe. A. 

 decollata, Chemn, (cxsxvi, 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 ai'ms 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, with a single central septum and broad margin. Recent, 

 Y sp. Fossil, 3 sp. Lias — Great Oolite ; Bi'itaiu. A. David- 

 soni, Moore (cxxxvi, 64, 65). 



Family STRINGOCEPHALIDJ^. 



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. 



Stringocephalus, Defrance, 1824. 

 Etym. — Strinx (stringos) , an owl ; cephale, the head. 

 Distr. — S. Burtini.1 Defrance (cxxxvi, 55, 56, 6(>, 67). 2 sp. 

 Silurian, Devonian ; Europe. 



Shell punctate ; suborbicular, with a prominent beak ; ventral 



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