No.iir.2. CAMIUtlAN nRACniOVODA—lVALCOTT. 405 



The material lor study is so limited it is difficult to make compari- 

 sons with other species. In form the ventral valves resemble that of 

 0. {L.) Uneolntti.s, 0. {L.) tarpa, and in some respects 0. {L.)(/ranvillcnsis, 

 with which it wouhl be more naturally comj^ared, owing- to its belong- 

 ing to the Appalachian faunai. 



Formation and locality. — Middle (?) Cambrian, St. Albans shale, in 

 limestone lentile a little west of the town of (leorgia, about a mile east 

 of Parker's (juarry; also a mile SSW. of Jlighgate Falls, Franklin 

 County, Vermont. 



Ti/pe.—l^o. L'T.'U.S, II.S.N.M. 



OBOLUS (LINGULELLA) HAYESI, new species. 



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

 obtusely acuminate and the dorsal valve -rimnded ovate; valves mod- 

 erately convex. Outer surface, as seen in casts, marked by fine, con- 

 centiic lines and stria' of growth; the iuTier surface had tine, radiating 

 stria; and scattcired pits or ])un('ta'. Tlu; shell a])pears from tlie casts 

 to have been of medium thickness and built up of several layers or 

 lamella'. 



The average length of the ventral valve is about 3.5 mm.; width 

 about 3 mm. The dorsal valves are a little shorter than the ventral 

 valves, the length and width being about the same, although some of 

 the shells are a little wider than long. 



Tlie casts of the interior of the ventral valve show a clearly defined 

 strong area, divided midway by the cast of a narrow pedicle groove, and 

 again by a sharp flexure line situated a little nearer the pedicle groove 

 than to the lateral margin. The stria' of growth vross the area i)arallel 

 with its base, arching over the cast of the pedicle furrow. The area 

 formed a thin shelf between the pedicle groove and the lateral margins, 

 the undercut extending back under the area, as shown in the cast, by a 

 thin projection of the imbedding rock over the area. The area of the 

 dorsal valve is of medium length and marked by stria; of growth and 

 rather clearly defined flexure lines. 



The cast of a ventral valve shows the visceral cavity (r) and rather 

 strong and long main vascular sinuses. In the dorsal valve the main 

 vascular sinuses are frequently outlined very beautifully on the siliceous 

 casts; the visceral area surrounded by the parietal band is clearly 

 defined, also the central and anterior lateral muscle scars, and in one 

 cast the transmedian muscle scars. 



Observations. — This very pretty species occurs quite abundantly on 

 the siliceous nodules imbedded in the Coosa shales. It resembles in 

 form (). {J J.) lamhorni and 0. (L.) tvillisi, but is a much smaller species. 

 The elongate visceral (cavity of the dorsal valve is also of the same type 

 as that oi" those species. The thickening in front of the visceral cavity 

 is similar to that which occurs in 0. niatinalis. In this character and 

 in its broadly o\ ate form it comes very close to the forms which are 

 referred to Oholits. 



