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, Sue. 

 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 ai>pcndages. 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 posilon of the branchiae. 



Numberless Terebratulse 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 cmarginated 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-|. In 



Thecidea, -De/., 



The pedicle seems to have been incorporated wil^ the small 

 valve 8. 



* M. Defrance distinguishes upwards of two hundred. 



-f- Anomia scobinafa, Gualt., 96, A ; — An. aurita, Id., lb., B ; — An. retusa; — An. 

 fruncata, Cbemn., VIII, Ixxvii, 711 ; — An. capensis, lb., 703; — An. pubescens, Id., 

 Ixxviii, 702 ; — An. defruncatu, lb., 705 ; — An. samjuinolenta, lb., 706 ; — An. vitrea, 

 lb., 707, 709 ; — An. dorsata, lb., 710, 711 ; An. psittacea, lb. 713 ; An cranium, &c. 



For the fossil species, see Eneyc. Method. Vers, pi. 239 — 246. 



X 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. 

 radiula, Fauj. Mont. St Pierre, pi. xxvii, f. 8. Fiutlier, and more precise observa- 

 tions arc requisite, to enable us to class the Magas of Sowcrby, the Striuoce- 

 PHALA of Defrance, and some other ucighbouriug groups. 



