ACEPHALA TESTACEA. 397 



PlagiostomAj Sowerb. 



The oblique shell of a Lima, flattened on one side; very small ears; 

 the valves more convex, striated, vpithout scales, the opening for the 

 byssus smaller(l). Found in formations anterior to chalk. 



Pachytes, Defr. 



Nearly the same form as that of the Pectinesj shell regular, with 

 small ears; a flattened transverse space between their summits, 

 which in one of the valves is marked by a deep triangular notch, in 

 which passed the ligament. Found in chalk(2). In the 



DiANCHORAj Sowerb., 



The values are oblique and irregular, one of them adherent and with 

 a perforated summit, the other free and with ears(3). 



PoDOPsis, Lam. 



Regular striated valves without opercular the summit of one of them 

 more salient, truncated and adherent, frequently very thick, and 

 forming a sort of pedestal to the shell(4). 



Although multivalve, we should approximate the 



Anomia, Brug. 



To the Ostreae. The Anomise have two thin, unequal, irregular 

 valves, the flattest of which is deeply notched on the side of the 

 ligament, which is similar to that of the Ostreae. The greater part 

 of the central muscle traverses this opening to be inserted into a 



scribes a fourth living species under the name o{ Hinnita Defrandi; M. Defrance 

 also admits two fossil species, the H. Cortesii, Blainv., Malac, pi. Ixi, f. 1, and the 

 H. Dubuissonii. 



(1) Flagiostoma gigas, Sowerb., Encyc. Method., Test, pi. 238, f. 3; Pl.lae- 

 vigatum. Parkins., Org. Rem., Ill, pi. xiii, f. 6; and the other species given by 

 Sowerby, IMin. Conch., pi. 113, 114, and382. 



(2) Puchytos spinosus, Fr. Sowerb., Cuv., Oss. Foss., II, Env. de Paris, pi. iv, 

 2, A, B, C, and IJlainv., Malac, pi. Iv, f. 2: Pack, hoperi, Sowerb., 380. 



(3) Dlanch. striata; D. lata, Sowerb., Min. Conch., pi. 80. 



(4) Podops. truncaia, Encyc. pi. 188; f. 2, 6, 7; Cuv., Oss. Foss.; Env.de 

 Paris, pi. V, f. 2. 



N.B. M. de Blainville considers these four last genera as more nearly related to 

 the Terebrutulx. M. Deshayes, on the contrary, Ann. des So. Nat. Dec. 1828, ap- 

 proximates them to the Spondyli. 



