352 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
nearly flat brachial valve, shorter pedicle interarea which is more steeply apsacline 
than that of H. tricenaria and much less inflated pedicle valve. 
This species is also suggestive of H. biconvexa but has a nearly flat brachial 
valve rather than a gently convex one; the pedicle valve is less swollen in 
H. biconvexa and the costae are somewhat more distantly spaced. 
HESPERORTHIS IGNICULA (Raymond) 
Plate 51, F, figures 27-34 
Orthis disparalis Bitt1ncs, Canadian Nat. Geol., vol. 4, p. 440, figs. 20a,b, 1850. 
Orthis ignicula RayMonp, Amer. Journ. Sci., ser. 4, vol. 20, p. 369, 1905; Ann. Carnegie Mus., 
vol. 7, No. 2, p. 236, figs. Io, II, IQII. 
Hesperorthis ignicula (Raymond) TwENHOFEL and WuitINnc, Geol. Soc. Amer. Special 
Pap. 11, p. 46, pl. 7, figs. 3-5, 1938. 
This species is generally fairly small for the genus, but the outlines and profile 
are typical. The ornamentation consists of high, narrowly rounded costae that 
appear in 2 generations, one at the beak and the other slightly anterior to it. 
Nevertheless, the costae are of about uniform size along the margins. The inter- 
spaces show a single costella. No pseudodeltidium was seen at the apex of the 
delthyrium and none was reported by Raymond. The cardinalia of the brachial 
valve are like those of Hesperorthis. Thus the entire expression of this species, 
internal and external, is that of Hesperorthis, and this is perhaps the earliest 
species of the genus. 
Types.—Lectotype: Carnegie Mus. 5453; paratype: Carnegie Mus. 5527; 
figured hypotypes: 109925a,b. 
Horizon and locahty.—Valcour formation in New York: Cystid Point, Val- 
cour Island, Plattsburg (15’) Quadrangle; on New York Highway 22, about 1 
mile southeast of Beekmantown, Rouses Point (15’) Quadrangle. 
HESPERORTHIS LONGIROSTRIS Cooper, new species 
Plate 52, A, figures 1-7 
Hesperorthis cf. H. tricenaria (Conrad) Butts, Virginia Geol. Surv. Bull. 52, pt. 2, p. 41, 
pl. 73, figs. 11, 12, 15 (not figs. 13, 14—Dinorthis sp.), 1942. 
Shell of about usual size for the genus, slightly wider than long; hinge slightly 
narrower than the greatest shell width which is at about the middle. Cardinal 
extremities varying from a right angle to slightly obtuse. Anterior commissure 
rectimarginate to very slightly sulcate. Lateral margins varying from nearly 
straight to very gently rounded; anterior margin fairly strongly rounded. Sur- 
face costate, with 27 to 30 strongly rounded costae separated by interspaces 
slightly narrower than the costae, fine radial costellae appearing in the inter- 
spaces and on the costae but too indistinct to enumerate. 
Pedicle valve with the greatest curvature in the posterior half; somewhat nar- 
rowly rounded medially in anterior profile; beak pointed, forming an angle of 
100° to 110°. Umbonal region narrowly rounded with steep umbonal slopes. 
Median region moderately swollen with steep slopes to the anterior and lateral 
