BRACmOPODA. 



279 



processes of other Terebratulas. From the upper part of these rods arises the 

 brachial support, consisting of a very slender calc-ribbon, which, somewhat as 

 in Waldheimia, first extends to the vicinity of the anterior margin, then bends 

 abruptly backward, inclining somewhat toward the center of the shell-cavity, 

 and is closed by a short, straight cross-piece, above which the ascending branches 

 project as short points ; this cross-piece and the upper part of the ascending 

 branches lie below the plane of the straight rods. While in the small valve 

 the hinge-muscle and the inner pair of dorsal pedicle-muscles are attached to 

 the callous process, the outer pair of pedicle-muscles appears to have been 

 fastened to the upper portion of the crura. The impressions of the adductors, 

 of which but two are discernible, lie somewhat above the middle of the valve, 

 in two cavities, often very deep, semicircular on their posterior margins, but 

 oblique and shallow in front. 



no. Ml. FIO. 202. 



' Uegatanteiit Archiaei, de Vernouil. 

 Fig. 201. An internal cast of the nmbonal region of the pedicle-valve. (SuBSS.) 



Fig. 20-2. The interior of the umbonal region of the brachial valve; showing the cardinal process. (De Vebneuil.) 



" In the large valve the muscular area is close about the umbo, and is similar 

 to that of the terebratuloids ; a middle elongate space corresponds probably to 

 the adductor muscles ; on either side of this, one recognizes the impressions of 

 the diductor muscles, and outside and somewhat behind these, though not 

 always clearly defined, are the areas of insertion of the ventral branches of the 

 pedicle-muscle, which also seems to lie on the inner surface of the dental 



plates. 



" On the inner surface of both valves may be distinguished four impressions 

 of trunk-sinuses, from which arise no dichotomous branches as in other tere- 

 bratuloids. The posterior part of the outer pair of these sinuses is in each 

 valve surrounded by the impressions of the genital organs, whose outer portion 



