564 CAMBRIAN BRACHIOPODA. 



to be all that is left to indicate the cardinal area; the central muscle scars are situated just 

 in advance of this depression and the anterior laterals at the front end of the visceral area ; the 

 position of the transmedian and outside lateral scars is indicated by an elongate scar near 

 the posterolateral margin, just in advance of the traces of the cardinal area. Vascular markings 

 unknown. 



This species differs from E. desiderata in having a thicker and more convex shell and has 

 a differently shaped visceral area in the dorsal valve. 



Formation and locality. — Lower Ordovician: (319)'' Limestone No. 1 of Billings's section; and (3191) limestone 

 of Billings's section; both at Point Levis, Province of Quebec, Canada. 



Subfamily NEOBOLIN^E Walcott and Soliuoliert. 

 Genus NEOBOIiTJS Waagen. 



[vioc, young; and Obolus. 



Neobolus Waag'en, 1885, Mem. Gaol. Survey India, Paleontologia Indica, ISth ser.. Salt Range Fossils, vol. 1, pt. 4, 



fas. 5, pp. 756-758. (Described and discussed as a new genus.) 

 Davidsonella Waagen [not Munibe-Chalmas, 1880], 1885, idem, pp. 762-764. (Described and discussed as a new 



genus.) 

 Neobolus Waagen, Oehlert, 1887, Manuel de conchyliologie, by Fischer, p. 1263. (Described in French, with figures 



of Neobolus warthi.) 

 Ldkhmina Oehlert, 1887, idem, p. 1265. (Described in French, with figures of " Lakhmina linguloides.") 

 Lakhmina Oehlert, Waagen, 1891, Mem. Geol. Survey India, Paleontologia Indica, 13th ser., Salt Range Fossils 



vol. 4, pt. 2, description of PI. II, figs. 3-4. (No text reference.) 

 Lakhmina Oehlert, Hall and Clarke, 1892, Eleventh Ann. Rept. State Geologist New York for 1891, pp. 234r-285. 



(Described.) 

 Neobolus Waagen, Hall and Clarke, 1892, idem, p. 245. (Described.) 

 Lakhmina Oehlert, Hall and Clarke, 1892, Forty-fifth Ann. Rept. New York State Museum for 1891, pp. 550-551. 



(Copy of Hall and Clarke, 1892a, pp. 234-235.) 

 Neobolus Waagen, Hall and Clarke, 1892, idem, p. 561. (Copy of Hall and Clarke, 1892a, p. 245.) 

 Lakhmina Oehlert, Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, pp. 28-30. (Described 



and discussed.) 

 Neobolus Waagen, Hall and Clarke, 1892, idem, p. 84. (Described and discussed.) 

 Neobolus Waagen, Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 72-76. (Described and discussed as 



below, with the exception of the paragraph describing the two text figures.) , 



Neobolus Waagen, Walcott, 1908, idem, vol. 53, No. 4, PL XI, and pp. 142 and 144. (Classification of genus.) 



General outHne of shells broad oval to subcircular; nearly equivalve, moderately convex. 

 Shell substance calcareocorneous and probably phosphatic, structure laminated. Surface with 

 concentric striation. Shell strong for its size and built up on its anterior and lateral margins 

 of several thin layers or lamellae. Apex of ventral valve small and slightly projecting over a 

 low false area that appears to have an open delthyrium. Apex of dorsal valve marginal. 



The interior of the ventral valve has a strong, rounded, central ridge extending from 

 the narrow area, about one-third the length of the shell, and a strong ridge on each side that 

 extends from the same point of origin as the central ridge obKquely forward nearly to the 

 frontal margin of the shell ; '' between the central ridge and the posterior portions of the lateral 

 ridges there are slightly concave shelves forming, with the central ridge, a triangular platform, 

 with an open space beneath the concave shelves; numerous radiating striee occur on the con- 

 cave shelves and the inner surface of the shell. 



Of the muscular impressions in the ventral valve, Waagen wrote [1885, p. 762] that 

 "nothing can be observed." Considered from the point of view of the Trimerellidse, this 

 may appear to be correct, but if we compare the muscle scars of Obolus with what appear to 

 me to be points of attachment of muscles in the specimen represented by Plate LXXXI, figure 

 2e, there is no difficulty in recognizing a few scars. Just beneath the outer extension of the 

 narrow area of the ventral valve there is a minute, clearly defined, elongate, oval space that 

 corresponds to the divided umbonal muscle scar in Oholus apoUinis Eichwald; near the outer 



a This is the locality from which the species is listed in the collections of the Geological Survey of Canada. Billings [lS62b, p. 71] also identifies 

 the species from No. 2 of his section. 



6 1 do not find any indication of the incurving of these ridges as described and illustrated by Waagen [1885, p. 762, PI. LXXXV, fig. 6]. 



