=. 199 7 — 
182. Arca (Arca s, sir.) tetragona Poli. 
N Taf. 47. Fig. 10—12. 
Concha elongata, ovato-rhomboidea, subaequivalvis, perinaequilatera, latere antico 
brevissimo, postico elongato, oblique truncato, haud emarginato; margo dorsalis strietus, 
utringue angulatus, antieus oblique declivis, basalis fere strietus, cum postico angulum 
formans; carina distineta ex umbone ad angulum decurrens. Superficies costis parvis 
numerosis radiantibus striisgue concentrieis subregulariter decussata, striis ad carinam 
subsquamosis, pallide rufescens, haud maculata, epidermide tenui subsquamosa, ad carinam 
in membranam pectinatam fissam elongata induta. Umbones anteriores, acuti, apieibus 
incurvis, distantibus; area magna, rhomboidea, obscure strigata, plana, ligamenti !/, areae 
tantum occupans. 
Long. 25, alt. 11, crass. 12 Mm. 
Arca tetragona Poli Testacea Siciliae II p. 137 t. 25 fig. 12. 13. 
— — Turton Dithyra britann. p. 167 t. 13 üig. 1. 
_ E= Lamarck-Deshayes Anim. sans vert. vol. 6 fig. 461. 
—_ _ Blainville Faune frangaise pl. 7 fig. 2. 
— E= Philippi Enum. Moll. Sieiliae I p. 57; II p. 42. 
- _ Reeve Conchologia icon. sp. 100. 
— —_ Forbes et Hanley British Moll. II p. 234 t. 44 fig. 9. 10. 
_ — Sowerby Illustr. index t. 8 fig. 10. 
— — Jeffreys British Conchol. II p. 180 t. 30 fig. 6. 
— _ Weinkauff Mittelmeer I p. 192. 
— — Hidalgo Moluscos mar. p. 132 t. 69 fig. 4..5. 
— — Kobelt Prodromus p. 411. — 
= = Buequoy, Dautzenberg et Dollfus Moll. Roussillon II p. 179 
t. 31 fig. 1—12. — 
—  tortuosa Pennant Brit. Zoolog. IV p. 97, nee L. 
—  fusea Solander mss. nee Brug. — Donovan Brit. Shells pl. 158 fig. 3. 4. 
— Noae Montagu, Pennant, Turton, nee Linne. 
— cardissa Lamarck Anim. sans vert. VI p.38. — ed. II. vol. VI. p. 463. 
_ —_ Dellessert Recueil pl. 11 fig. 14. 
—  navicularis Deshayes-Lam. Anim. sans vert. VI. p. 461 nec Brug. 
_ _ Loven Index p. 187. 
_ _ Brusina Contr. fauna Dalm. p. 102. 
—  britannica Reeve *) Concholog. icon. sp. 98. 
*) A. testa oblique trapeziformi, lateribus superne angulatis, latere antico brevissimo, attenuato, 
postico oblique angulato, inferne acuminato, carina obliqua ab umbone ad marginem decurrente; fuscescente; 
striis longitudinalibus et transversis decussata; ligamenti area latiuscula, umbonibus incurvatis, — 
