ACEl'HALA TESTACEA. 
87 
Plagiostoma, Sowerb., 
The oblique shell of a Lima, flattened on one side ; very small ears ; 
the valves more convex, striated, without scales, the opening for the 
byssus smaller * * * § . Found in formations anterior to chalk. 
Pachytes, Defr. 
Nearly the same form as that of the Pectines; 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 f. In the 
Dianchora, Soioerb., 
The valves are oblique and irregular, one of them adherent and with 
a perforated summit, the other free and with ears];. 
PoDOPSis, Lam. 
Regular striated valves without opercula ; the summit of one of them 
more salient, truncated and adherent, frequently very thick, and form- 
ing a sort of pedestal to the shell §. 
Although multivalve, we should approximate the 
Anomia, Brug. 
To the Ostreae. The Anomiae 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 
third plate that is sometimes stony and sometimes horny, by which 
the animal adheres to foreign bodies, and the remainder of it (the 
muscle) serves to join one valve to the other. The animal, — Echion, 
Poll, has a small vestige of a foot, similar to that of a Pecten, which 
slips between the emargination and the plate that closes it, and per- 
haps serves to direct water to the mouth which is close to it [|. 
These shells are found attached to various bodies like the Ostrem. 
They are found in every sea 
* Plagiostoma gigas, Sowerb., Encyc. Method., Test., pi. 238, f. 3 ; — PI. la- 
vigatum, Parkins., Org. Rem.. Ill, pi. xiii, f. 6 ; and the other species given by 
Sowerby, Min. Conch., pi. 113, 114, and 382. 
-t Pachgtos spinosus, Fr. Sowerb., Cuv., Oss. Foss., II, Env. de Paris, pi. iv, 2, 
A, B, C, and Blainv., Malac., pi. iv, f. 2 : Pack, hoperi, Sowerb., 380. 
X Dianch, striata; — D. lata, Sowerb., INIin. Conch., pi. 80. 
§ Podops. truncata, 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 Terebratultp. M. Deshayes, on the contrary, Ann. des Sc. Nat. Dec. 1834, it 
proximates them to the Spondyli. 
II This foot escaped the notice of M. Poli. 
Anomia ephippium, Gm. ; — A. cepa ; — A. electrica ; — .4. squamulu; — A. uai- 
leala ; — A. squama; — .{.punctata ; — A. undulata , — and the species added by Bru- 
gi^res, Encyc. Method., Vers., I, 70 , et scq. ; and pi. 170, 71. 
The other Anomies of Gmelin are Placuncc, Tcrebraluhr, and JIgalec. 
