BRACHIOPODA. 
117 
Terebratula, Brug. 
Two unequal valves united by a hinge; the summit of one, more 
salient than the other, is perforated to permit the passage of a fleshy 
pedicle which attaches the shell to rocks, madrepores, other shells, &c. 
Internally, a small bony piece of frame- work is observed, that is some- 
times very complex, composed of two branches which articulate with 
the unperforated valve, and that support two arms edged all round 
with a long close fringe, between which, on the side next to the large 
valve, is -a third, simply membranous and much longer appendage, 
usually spirally convoluted, and edged, like the arms, with a fine and 
close fringe. The mouth is a small vertical fissure between these 
three large appendages. The principal part of the body, situated 
near the hinge, contains the numerous muscles which reach from one 
valve to the other, and between them are the viscera, which occupy 
but little space. The ovaries appear to be two ramified productions, 
adhering to the parietes of each valve. I have not yet been able to 
ascertain exactly the positon of the branchiae. 
Numberless Terebratulae are found fossil or petrified, in certain 
secondary strata of ancient formations* * * § . The living species are less 
numerous f. 
The shell of some is transversely broader or longer, in a direction 
perpendicular to the hinge, with an entire or emarginated contour, 
with two or several lobes; some of them are even triangular; the sur- 
face is smooth, sulcated in radii, or veined ; they are thick or thin, and 
even diaphanous. In several of them, in lieu of the hole in the 
summit of the thin valve, there is a notch, and this notch is sometimes 
partly formed by two accessory pieces, &c. It is probable that when 
better known, their animals will present generic differences. Already 
in the 
Spirifer, Sowerby, 
Two large cones have been recognized, formed of a spiral thread, 
which appear to have supported the animal J, In 
Thecidea, Def., 
The pedicle seems to have been incorporated with the small 
valve §. 
* M. Defrance distinguishes upwards of two hundred. 
•f- Anomia scohinata, Gualt., 96, A; — An. aurita, Id., Ib., B ; — An. refusa; — An. 
ii-uncata, Chemn., VIII, Ixxvii, 711 ; — An. capensis, Ib., 703 ; — An. pubescens, Id., 
Ixxviii, 702; — An. detruncata, Ib., 705 ; — An. sanguinolenta, Ib., 706; — An. vitrea, 
Ib., 707, 709 ; — An. dorsata, Ib., 710, 711 ; An. psiitacea, Ib. 713 ; An cranium, &c. 
For the fossil species, see Encyc. Method. Vers, pi. 239 — 246. 
J For this genus see Sowerb., Min. Conch, and the article Spirifere of M. De- 
france, Diet, des Sc. Nat. t. L. 
§ Thecidea mediterranea, Risso, Hist. Nat. de la Fr. Merid., IV, f, 183; — Th. 
radiata, Fauj. Mont. St Pierre, pi. xxvii, f. 8. Further, and more precise observa- 
tions are requisite, to enable us to class the Magas of Sowerby, the Striuoce- 
FHALA of Defrance, and some other neighbouring groups. 
