OBOLIDiE. 527 



margin of the visceral area. This ridge corresponds to a median groove passing anteriorly 

 into the heart-shaped cavity. There are no clearly defined muscle scars in any specimen in 

 the collection, although the trapezoidal area in the ventral valve, in which the central, middle, 

 and outside lateral muscle scars usually occur, is fairly well preserved in one sjDecimen. None 

 of the casts of the dorsal valve show more than the cast of the median ridge or septum. Of 

 the markings left on the shell by the vascular system only the main vascular sinuses have 

 been preserved on the cast of the ventral valve. 



Ohservations. — This is a small but striking species that occurs in the sandstones east of 

 the Adirondack Mountains. In outline and form it may be grouped with LiiiguLella ferruginea 

 Salter and L. bellula (Walcott) (PI. XIX). It is a larger and more acuminate shell than 

 L. ferruginea, and its dorsal valve is distinguished from that of L. hellula by being shorter 

 and broader anteriorly. It occurs quite abundantly in the thin beds of hard sandstones at 

 Ausable Chasm, below Keeseville, Essex County, New York, associated with Ptychoparia minuta 

 and L. (Lingulepis) acuminata (Conrad) (?). The interior of the ventral valve resembles typical 

 forms of Obolus more nearly than the typical forms of Lingulella. This may be'due to the state 

 of preservation or it may be that, despite the Lingula-\\\<ie outlines of the valves, it is more a 

 true Oholus in its interior markings as these are developed in 0. matinalis (Hall). (Compare 

 PI. VIII, fig. le, with PL XXVII, fig. 1.) 



Whitfield [1884, p. 142] referred the species to the genus Oholella. There is a strong 

 resemblance between the dorsal valve of the species and that of some of the species of Oholella, 

 but a careful study of a large amount of material shows that this resemblance is confined to 

 the dorsal valve. He also refers "Oholella nitida" Ford to this species, but "0. nitida" is a 

 true Acrotreta and occurs in the lower portion of the Olenellus fauna of the Lower Cambrian, 

 and Lingulella prima (Hall) is from the Upper Cambrian. 



Dwight [1886, p. 208] mentions "Oholella (Lingulella) prima" as occurring in "Potsdam" 

 strata at Poughkeepsie, New York, but inasmuch as he does not describe the specimen, and 

 the form has not been found in other extensive collections that have been made there, the 

 reference is considered as exceedingly doubtful. I think Dwight had small specimens of the 

 dorsal valve of Lingulella (Lingulepis) acuminata (Conrad), which occurs at the locality at 

 Poughkeepsie. 



Formation AND LOCALITY. — Tipper Cambrian : {n)"- Sandstone near the water below the falls at the high bridge, 

 and also at several horizons in the section, the highest point being 70 to 75 feet {21 to 23 m.) above the water, in Ausable 

 Phasm; (367f) sandstone at French Creek, 1 mile (1.6 km.) east of Keeseville; (367g) sandstone in the bed of the 

 brook, in the suburbs of Port Henry; (367h) Rosses Bridge, 4 miles (6.4 km.) west of Essex; (136) Potsdam sandstone 

 in bank of stream opposite the first switch on the Port Henry and Maine Railroad out of Port Henry; and (338t^ 

 Potsdam sandstone in Ausable Chasm, below Keeseville; all in Essex County, New York. 



^^ 



Lingulella? primleva Hicks. 

 Plate XXXI, figures 5, 5a. 



Lingulella primxva Hicks, 1871, Quart. Jour. Geol. Soc. London, vol. 27, p. 401, PI. XV, figs. 13 and 14. (Described 



as a new species.) 

 Lingulella primxva Hicks, Salter and Etheridgb, 1881, Mem. Geol. Survey Great Britain, vol. 3, 2d ed., p. 538. 



(Localities mentioned.) 

 Lingulella primxva Hicks, 1881, Popular Science Review, new ser., vol. 5, p. 297. (Mentioned only.) 

 Lingulella primxva Hicks, Davidson, 1883, British Fossil Brachiopoda, vol. 5, pt. 2, p. 208, PI. XVII, figs. 33 and 



34. (Described and discussed. Fig. 33 is drawn from the specimen figured by Hicks, 1871, PI. XV, fig. 14. 



Figs. 33 and 34 are reproduced in this monograph, PL XXXI, figs. 5a and 5, respectively.) 



This species is rather doubtful, owing to its condition of preservation, which renders it 

 quite difficult to make any comparison with other described species. It occurs in association 

 with L. ferruginea Salter, but is a much larger species. 



Formation and locality. — Middle? Cambrian: (366c) "Caerfai group" [Salter and Etheridge, 1881, p. 538'] at 

 Caerfai, Nuns Sill, and Porthclais Harbor, all south of St. Davids; and (318i) red shales of the Caerfai group at St. 

 Davids; both in South Wales. 



o77 is the type locality, though the specimens in the United States National Museum collections to which that number is assigned 

 were collected later than the type specimens. 



