N0.1229. CAMBRIAN BRACHIOPODA—WALCOTT. 685 



In view of the imperfect state of preservation, a determination can 

 be based only on the outer form, whose habit agrees with the American 

 species from the Cambrian limestone of Troy. 



Dr. Bornemann kindly sent me two specimens of this form. They 

 suo-o-est (JljoJtUa cra.s.sa in form and outline, but the material is too 

 imperfect to enable me to identify the species or genus. I find in one 

 specimen indications of the presence of a high area that rises slightly 

 above the plane of the ventral valve. In two there is nothing to sug- 

 gest the foramen, which is usually well preserved in the veiitral valve 

 of species of OholeUa atlantku. As the material is probably from the 

 Middle Cambrian, a provisional reference is made to Obolus. 



Subgemis LINGULELLA. 



OBOLUS (LINGULELLA) BELLUS Walcott. 



Oholus {LuKjuMln) hdlns AValcott, Proc. U. S. Nat. Museum, 1898, XXI, p. 397. 

 LingideUu concmna Matthew, Bull. Xat. Hist. Soc, Xew Brunswick, 1900, IV, 



p. 273, pi. V, tigs. 2a-b. 

 i///(/H/« .-^ ?('»s Matthew, Bull. Xat. Hist. Soc, Xew Brunswick, 1900, p. 274, pi. v, 



tigs. 3a-b. 



General form ovate, with ventral valve obtusely acuminate; dorsal 

 valve broad ovate; valves moderately convex, so far as can be determined 

 from the somewhat compressed specimens as they occur in the sandy 

 shales. 



Surface of shell bearing numerous concentric lines of growth, with 

 exceedingly fine, slightly irregular striae on the interspaces between 

 the stronger concentric lines that form a surface somewhat like that of 

 0. (Z.) elhi. Owing to the roughened surface formed by the line stria?, 

 the outer layer of the shell adheres to the arenaceous matrix, leaving 

 the shiny inner layer on the shell. This is marked by concentric and 

 numerous line radiating stria?. 



The shell is apparently thin, and is formed of a very thin outer layer, 

 with one or more thin inner layers or lamella?. The ca.sts of the 

 interior surface of the ventral valves show numerous papilhi? arranged 

 in concentric lines on the posterior half of the shell. These correspond 

 to the punctfe of the inner surface. 



A large ventral valve has a length of 15 mm. ; width 9 mm. ; and a 

 dorsal valve 13 mm. in length has a width of 10 mm. The specimens 

 in the collection average from 2 to 3 mm. smaller than those measured. 



The cast of the area of the ventral valve shows that it was rather 

 long and extended well out on to the cardinal slope; it is divided mid- 

 way by a strong pedicle furrow, and toward the lateral margin by a 

 narrow flexure line. The area is marked by fine stria of growth 

 parallel to the margin. The area of the dorsal valve is rather short, 

 but it extends laterallv well out on the cardinal slopes. The shallow 



