N0.1395. CAMBRIAN BRACHIOPODA—WALCOTT. 279 



by dental plates that extend to the bottom of the valve and bound the 

 umbonal cavity (pseudospondyliinn). The only traces of the vascular 

 system are the bases of strong vascular trunks. The adductor muscle 

 scars appear to have been carried into a very narrow space on an ele- 

 vated ridge between the deep impressions made by the main vascular 

 trunks; in another specimen the points of attachment of the muscles 

 are well advanced into the valve. 



In the interior of the dorsal valve a cast of the pseudocruralium 

 appears to have a small, cardinal process, or callosity, but it is too 

 doubtful to serve as basis for a statement that the cardinal process is 

 present; there are traces of a median septum shown on the central 

 ridge toward the center of the valve. The cardinal process occurs 

 in the anterior half of the umbonal cavity. The casts of the interior 

 show that the crura are short and well defined, with relatively strong- 

 dental sockets beside them. The only traces of the muscle scars 

 observed are those of the adductor. 



OhservationH. — The exterior surface and size of this shell recalls O. 

 {Fiiikslnhurgia) osceola. It difi'ers, however, in the accuminate ventral 

 angles and strongly convex dorsal valve. In form the elongate cardi- 

 nal angles relate this species to BlUingseUa {Otn.sla) sandheryi., but in 

 surface and interior markings it materially differs from the latter. 



Formation and locality. — Upper Cambrian. St. Croix sandstone at 

 Trempealeau, Devils Lake, Osceola Mills, Wisconsin. Minneiska, 

 Minnesota. 



ORTHIS (FINKELNBURGIA) OSCEOLA, new species. 



The general form of this species is similar to that of P. remnicha., 

 except that it is usually more transverse. It is a smaller shell, aver- 

 aging for the ventral valve a height of 8 mm. and width of 11 mm., 

 while P, remnicha averages 12 mm. in height and 14 to 16 mm. in width 

 in the adult shell. The radiating cost* are more uniformly rounded 

 and regular and more numerous, except when compared with the 

 variety texana. The shell of O. (P.) osceola is thick like other forms 

 of the genus with a result that the vascular markings are definitely 

 outlined. In one specimen the anterior and posterior diductor scars 

 are beautifuUj'^ shown; also the large main vascular sinuses so charac- 

 teristic of man}^ species of Billmgsella. The adductor scars, cardinal 

 process and median septum are well brought out in a cast. Some of 

 the dorsal valves approach quite closely to those of P. retntucha 

 sidcata. 



J^ormation and locality. — Upper Cambrian. St. Croix sandstone, 

 Trempealeau; Menomonie, one-half mile southeast of court-house; 

 Mazomanie; Osceola Mills; Lodi, about one-third of a mile west of 

 railroad station, Wisconsin. Just below fJiceUocephalus minnesotensis 

 bed, Winona, Minnesota. 



