NO. 1152. CAMBRIAN BRACHIOPODA—WALCOTr. 407 



As far as may be determiued from the casts, the outer surface is 

 marked by concentric lines and strise of growth and the inner surface 

 by radiating striae and concentric lines of growth and scattered pits or 

 punct;t. The shell appears to have been rather thick and built up of 

 a thin outer layer and numerous lamelhe that over tlie anterior two- 

 thirds of the shell were oblique to the outer layer; the edges of the 

 lamelhe show very phiinlj^ when the outer layer is removed. 



The area of the ventral valve, as shown by casts of the interior, is of 

 medium length, divided midway by a narrow elevated cast of the 

 pedicle furrow, and again by a narrow flexure line about half way 

 between the pedicle groove and the lateral margin; i'tria* of growth 

 cross it parallel with the base. The area of the dorsal valve is rela- 

 tively long, with the flexure lines clearly defined. The interior niark- 

 ings shown in the cast of the ventral, valve are the main vascular 

 sinuses and the outline of the visceral area; in the dorsal valve only 

 traces of the visceral area and main vascular sinuses have been 

 observed. 



Observations. — This species appears to be more nearly related to 0. 

 (L.) tarpa than any other of the Middle Cambrian forms. It is a 

 smaller shell than 0. (L.) tarpa ;iud less acuminate. It has the outline 

 of some of the species of the Atlantic Basin fauna, such as 0.{L.))'ad>tlus, 

 but it does not appear to be specifically identical with any of them. 



Formation and locality. — Middle Cambrian, Kome formation, 2i miles 

 sonth of Eome, Georgia, where it occurs abundantly in a layer of 

 shaly sandstone. 



Type.— Bo. 27321, U.S.N^.M. 



OBOLUS (LINGULELLA) LAMBORNI, var. MINIMUS, new variety. 



This variety in its ventral valve closely resembles the adult forms of 

 the ventral valve of 0. {L.) lamhorni. The dorsal valve also has the 

 same general form as most of the dorsal valves of the species. In 

 comparing, however, the young specimens of the same size with the 

 variety minimus the ventral valves appear to be more obtuse in the 

 young of 0. [L.) lamhorni. 



All of the specimens occur as casts in a somewhat decomposed light- 

 colored buft" shale. 



Format ion and locality. — Uiy-per Cambrian, Eogersville shale, 3J miles 

 SSW. of Eogersville, Hawkins County, Tennessee. 



Tijpe.—l^o. 27322, U.S.N.M. 



OBOLUS (LINGULELLA) LEOS, new species. 



Shell small; general form elongate ovate, with the ventral valve 

 subacuminate. The valves are rather strongly convex in the narrow 

 form of the species. Average length of a ventral valve 5 mm., the 

 largest ventral valve has a length of mm.; the dorsal valve is 

 somewhat shorter. The width of the valves varies considerably in 



