BRACHIOPODA, 433 



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 sometimes very complex, composed of two branches which arti- 

 culate 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 rami- 

 fied productions, adhering to the parietes of each valve. I have not 

 yet been able to ascertain exactly the position of the branchiae. 



Numberless Tercbratulse are found fossil or petrified, in certain 

 secondary strata of ancient formations(l). The living species are 

 less numerous(2). 



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 

 surface 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. Sec. It is probable 

 that when better known their animals will present generic differ- 

 ences. Already in the 



Spirifer, Sowerby, 



Two large cones have been recognized, formed of a spiral thread, 

 which appear to have supported the animal(3). In 



(1) M. Defrance distinguishes upwards of two hundred. 



(2) Ancymia scobinata, Gualt., 96, A; — An. aurita, Id., lb., B; — dn. retusa,- — v?n. 

 truncata, Chemn., VIII, Ixxvii, 711; — An. capensis, lb., 703; — Jin. pubescens. Id., 

 Ixxviii, 702; — An. detruncata, lb., 705; — An. sanguinolenta, lb., 706; — An. vitrea, 

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



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



(3) For this genus see Sowerb., Min. Conch, and the article Spirifere of M. 

 Defrance, Diet, des Sc. Nat. t. L. 



Vol, II.— 3 E 



