boleuiilae. — Mesodesiuatidae. 141 



lariter subtilissime striata et iiiedio radiata, pallide lutescens, epidermide irides- 

 cente tecta ; pars anterior brevis , margo superus et inferus fere paralleli ; area 

 dorsalis colore pallidiore insignis; umbones obtusi, ad ^6 longit. siti. — Long. 

 >^0 nim. 



Distrib. : Atlanticum a Guinea ad Magnae Britanniae partem meridionalem. 



Habit. : — 20 org. prof. ; litora Hispaniae : Algesiras (Hidalgo), Slalaga 

 (McAxDKEW, Jeffreys), Valencia, Peniscola, Barcelona (Hidalgo); Alger, Bona 

 (Deshayes, Weixkauff) ; litora Galliae (Petit, Dubreuil), Roussillon, la Nou- 

 velle (Locard), la Franqui (PSpratx), Cette (Graxger), Pabwas (Locard), Aigues- 

 Mortes (CLfiMENx), le Grau du Roi, Martigues (Locard), Marseille (Ancey), le 

 Prado (^[ariox), ins. Hyeres (Locard) ; Xizza (Risso) ; litora pedemontana (Jekf- 

 reys) ; Corsica (RfiyuiEx), golfe de Valinco (Payraudeau) ; Spezia (Taitarone- 

 Caxefri) ; Livorno (Appf-lius) ; Napoli (Scacchi) ; Sicilia : Catania, Alicata (Phi- 

 Lippi), Catania, Palermo, Trapani (Aradas et Benoit); Adria: Venezia (G. v. Mar- 

 TENS , rar. , Brusina) , Zara (Sandri) , Trieste (Stossich) , Sebenico (Brusixa) ; 

 Morea (Deshayes) ; Aegyptus (Ehrexberg). 



10. Subordo. Myacea (Stol.) Fischer. 



Siphones elongatuli, ex parte aut omnino connati, epidermide coriacea tecti ; 

 brauchiae uon in siphones porrectae ; pes brevis lingui- aut digitiformis ; adduc- 

 tores duo; testa postice liians, epidermide coriacea tecta, cartilagine interna con- 

 juncta ; cardo dentibus paucis aut nullis, saepe ligamentum externum. 



24. Fam. MESODESMATIDAE Fischer. Margines pallii simplices; siphones 

 divergeutes, basi tantum conjuncti, orificiis papillosis ; pes magnus triangulus, sine 

 bysso ; palpi trigoni; branchiae binae utrinque inaequales, exterua appendiculata; 

 testa aequivalvis, trigona, cuneiformis aut ovalis, solida, chiusa ; umbones opistho- 

 gyri ; cardo plerumque utrinque dente singulo ante foveam ligamentalem , fere 

 semper dentibus lateralibus. 



Mesodesma Desh. Margines pallii laevcs; siphones ci/lindrici distincti, sat 

 eloncfati, analis tuberculis conicis, branchialis pinnatus; pes lonr/us, compressus, fri- 

 anyuhis; palpi trianr/uli ; branchiae vahle inaequahs; testa orata, transecrsa aut tri- 

 anyuta, crassa, clausa, partc a)itica lonr/iore; cardo fovca lir/anientali mcdiana anr/usta, 

 prominula et dentibus primario dupMci aut bifido et lateralibus anticis et posticis, 

 dr.rfra dupHeibus, sinistra simplicibus, lir/amentum internum. 



1. M. corneum P^tit {Mactra cornea Poli, Donax plebeja Penn., Amphi- 

 desma donaciUa Lam., A. corncum Jeffr., Donacilla Lamarcli Phil., 1). donacilla 

 Chexu). Testa ovato-triangula, crassa, transversa, inaequihitera, postice brevior, 

 margine integro , laevis , tenuissime transversim striata , luteo-albida aut lutea, 

 ])lerumque fusco varie radiata et strigata, colore pervariabili; cardo dentibus si- 

 nistra 3 — 4, postico majore ; sinus pallialis parvus, ovatus. — Long. 20 mm. 



Distrib. : Atlanticum lusitanicum ; Pontus. — Fossilis in stratis tertiariis. 



Habit. : — 2 org. prof. ; litora Hispaniae: Gibraltar, Mahiga (McAxdrew), 

 Barcelona, Mataro; Mahon (Hidalgo); Alger, Arzew, Bone, Lacalle (Deshayes); 

 litora Galliae (Petit, Dubreuil), Roussillon (Locard), Aigues-Mortes (CLfiMENT), 

 St. Raphael , St. Tropez , sin. Juan (Doublier , Gay) , Cannes (Dautzenbebg) ; 

 Nizza (VfiBANY); litora pedemontana (Jeffreys); Corsica (Payraudeau, R^^quien) ; 

 Sardinia: Bonifacio (Rolle); Spezia (Tapparone-Canefri) ; Napoli (Scacchi, Phi- 

 Lippi); Sicilia: Palermo. Cefalii, rar. (Philippi), frequ. (Aradas et Benoit); Ta- 

 ranto (Salis) ; Adria: Trieste, Ossero (Stossich), Rovigno (Stossich, Wimmer), 

 Zara (Sandri), Curzola (Heller); Morea (Deshayes); mare Aegeum (Forbbs). 



