OBOLID^. 505 



the northern part of Easton Station, 3 miles (4.8 km.) south of Greenwich, Cambridge quadrangle (U. S. Geol. Survey); 

 all in Washington County, New York. 



(29) Limestone just above the bridge at the Stockport paper mill, on Kinderhook Creek; and (Ob) limestone 

 near North Chatham in the northern part of the Kinderhook quadrangle (IT. S. Geol. Survey); both in Columbia 

 County, New York. 



(25a) Limestone on the Hall (Donaldson's) farm, 2 miles (3.2 km.) east of Swanton, Franklin County, Vermont. 



LiNGULELLA HAYESI (Walcott). 



Plate XXV, figures 1, la-j. 



Obolus {Lingulella) hayesi Walcott, 1898, Proc. U. S. Nat. Mus., vol. 21, pp. 405-406. (Described and discussed 

 as a new species, essentially as below.) 



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

 dorsal valve rounded ovate; valves moderately convex. Outer surface as seen in casts marked 

 by fine, concentric lines and striae of growth; the inner surface had fine, radiating striae and 

 scattered pits or punctje. The shell appears from the casts to have been of medium tliickness 

 and built up of several layers or lamellae. 



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. 



The 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 sharp flexure lines situated a 

 little nearer the pedicle groove than to the lateral margins. The striae of growth cross the 

 area parallel with its base, arcliing 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 embedding rock over the area. 

 The area of the dorsal valve is of medium length and marked by striae of growth and rather 

 clearly defined flexure lines. 



The cast of a ventral valve shows the visceral cavity 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, aJso 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 

 embedded in the Conasauga ("Coosa") shale. It resembles in form Oholus lamhorni (Meek) 

 and Oholus mllisi (Walcott), but is a much smaller species. The elongate visceral cavity of 

 the dorsal valve is also of the same type as that of those species. The thickening in front 

 of the visceral cavity (PI. XXV, fig. lb) is similar to that which occurs in Obolus matinalis 

 (Hall) (PI. V, fig. Id). In this character and in its broadly ovate form it comes very close 

 to the forms which are referred to Obolus. 



The specific name was given in honor of Dr. C. W. Hayes, at that time chief geologist of the 

 United States Geological Survey. 



Formation and locality. — Middle Cambrian : (90x and 94a) <^ In and attached to the outer surface of siliceous 

 nodules in the Conasauga ("Coosa") shale, Coosa Valley, east of Center, Cherokee County, Alabama. 



Lingulella heberti Barrois. 

 Plate XXXIX, figures 11, lla-c. 



Lingulella heberti Barrois, 1882, Mem. Soc. geol. du Nord, vol. 2, pp. 185-186, PI. IV, iigs. 3a-d. (Described and 

 discussed in French as a new species; see below for translation. Figs. 3a-d are reproduced in this monograph, 

 PL XXXIX, figs. 11, lla-c, respectively.) 



The original description by Barrois follows: 



Shell corneous, regular, elongated, slightly convex, scarcely inequivalve. Enlarged in the pallial region where 

 the outline is rounded; pointed at the beaks; longer than wide. Marked with well-developed concentric lines of 



a 90x is Ihe type locality. 



