Arca scapha Issel Mal. mar rosso p. 88. 
— Pharaonis Fischer Journal de Conchyliol. XIX. p. 213. — 
Hab. mare rubrum. 
Jedenfalls gehören nicht alle scapha-Formen aus dem rothen Meer zu A. Pha- 
raonis; das Senckenbergische Museum besitzt ganz typische Exemplare, von Rüp- 
pel mitgebracht. 
11. Arca (Scapharca) bifrons Carpenter. 
„A. t. turgida, subquadrata, tenui, maxime inaequivalvi, postice angulata, umboni- 
bus haud distantibus; alba, epidermide laevi, olivacea induta; costis eireiter 30, in testa 
juniore omnibus laevibus, in adultis solum 8—10 antieis, reliquis laevibus; costis ventrali- 
bus in valva minore parvis, rotundatis, interstitia haud aequantibus; in valva majore pla- 
natis, subobsoletis, interstitiis minimis; ligamento solido, aream rhomboideam implente; 
dentibus cardinis in linea curva, parvis; margine valvae majoris effoso, valvam alteram 
reeipiendo; costis propter tenuitatem intus monstrantibus. — Long. 1,55, lat. 1,73, alt. 
1,32%. — { 
Arca bifrons Carpenter Mazatlan Shells p. 154. 
Hab. Mazatlan (Mus. Cuming). — 
12. Arca (Byssoarca) vespertilio Carpenter. 
B. t. oblonga, compressa, postice tumidiore, expansa; valde inaequilaterali, margini- 
bus subrotundatis, hiatu pedis modico, margine ibi ineurvo; umbonibus subappressis ; 
ligamento longo, angusto, antice brevi; superficie radiatim striata, etriis subimpressis, 
lineis inerementi vix decussatis; rubro-fusca, intus maculis duabus ab umbonibus radianti- 
bus; epidermide lamellis concentrieis antice squamosis, postice brevibus; setis interstitia 
decurrentibus, in lamellis imbutis; huc et illuc lineis setarum validis, longis, maxime 
latere postico, ubi semitubulares sunt; dentibus haud parvis, haud numerosis, lineis valde 
ineurvis, antica brevi. — Long. O. 76, lat. 1,5, alt. 0,87. — 
Byssoarca vespertilio Carpenter Mazatlan Shells p. 140: 
Hab. Mazatlan, extremely rare. — 
13. Arca Bronnii Philippi. 
A. testa ovata, parum inaequivalvi, valde inaequilatera, alba, epidermide fusca inter 
costas squamosa vestita; extremitate antica rotundata, postica oblique producta; margine 
