186 THE DEVONIAN OF MISSOURI. 



Bilobites various Beecher, 1891, Am. Jour. Sci., 3rd ser., vol. XLII, p. 52, pi. I, figs. 



3-27. 

 Bilobites varcius Hall and Clarke, 1892, Pal. N. Y., vol. VIII, pt. I, pp. 204, 205, 223, 



pi. Vb figs. 15-19. 

 Bilobites varica Weller 1903, Pal. N. J., vol. Ill, p. 306, pi. XXXV, figs. 14-18. 

 Bilobites various Dunbar, 1919, Tenn. Geol. Surv., Bull. 21, pi. 2, fig. 4. 



Description — "Shell subcordiform ventricose, deeply bilobed at the base, with a 

 deep sulcus upon each valve reaching to the beaks; hinge line short. Area common to 

 both valves; that of the ventral valve higher. Foramen high and narrow. Ventral 

 valve acuate, ventricose on each side of the" sinus. Dorsal valve gibbous on each side the 

 mesial sinus; each lobe becoming angular towards the beak, and compressed toward the 

 cardinal extremities. Surface unequally striated; a few distant striae being visible to 

 the naked eye, while under a lens the interspaces are seen to be distinctly striated. Fine 

 concentric striae cross the radiating striae, and become conspicuous towards the base 

 of the shell."— Hall, 1859. 



Superfamily Strophomenacea 



Family Strophomenidae 



Genus Leptaena Dalman 



Leptaena rhomboidalis (Wilckens) 



Plate 46, figures 26-32 



Conchita rhomboidalis Wilckens, 1769, Nachricht von selten Versteinerungen, p. 77 



pi. VIII, figs. 43, 44. 

 Strophomena rugosa Hall, 1859, Pal. N. Y. vol. Ill, p. 195, pi. XIX, figs, la-y, 1861. 

 Leptaena rhomboidalis Hall and Clarke, 1892, Pal. N. Y., vol.. VIII, pt. I p. 279, pi. 



VIII figs. 17-31; pi. XVa, figs. 40-42; pi. XX, figs. 21-24. 

 Plectambonites rhomboidalis Keyes, 1894, Mo. Geol. Surv., vol. V, p. 70, pi. XXXIX, 



fig. 6.' 

 Leptaena rhomboidalis Girty, 1899, U. S. Geol. Surv., 19th Ann. Rept., pt. Ill, p. 563. 

 Leptaena rhomboidalis Clarke, 1900, N. Y. State Mus., mem. 3, p. 57. 

 Leptaena rhomboidalis Weller, 1903, Pal. N. J., vol. Ill, pp. 278, 302, pi. XXVII, fig. 9 



pi. XXXIII, fig. 10. 

 Leptaena rhomboidalis Shimer, 1905, N. Y. State Mus., Bull. 80, p. 240. 

 Leptaena rhomboidalis Clarke, 1908. N. Y. State Mus., mem. 9, pt. 1, pp. Ill, 116, 183, 



pi. 34, figs. 1-3. 

 Leptaena rhomboidalis Clarke, 1909, N. Y. State Mus., mem. 9, pt. 2, pp. 45, 122, 



pi. 10, figs. 1-6. 

 Laptaena rhomboidalis Maynard, 1913, Md. Geol. Surv., L. Dev., p. 308, pi. LVI, 



figs. 13-17. 

 Laptaena rhomboidalis Dunbar, 1919, Tenn. Geol. Surv., Bull. 21, pi. 2, fig. 17. 



Description — "Shell varying from semioval to semicircular. Hinge line equalling 

 or greater than the width of the shell below; cardinal extremities often much extended. 

 Dorsal valve flat or slightly concave in the upper part, and abruptly curving or inflated 

 towards the front; beak prominent, perforate at its apex, and filling a deep sinus in the 

 opposite valve. Ventral valve slightly convex or nearly flat in its upper part, and some- 

 times even concave; convex upon the umbo, often perforate near the beak; abruptly 

 deflected or geniculate towards the front; cardinal area narrow, linear, partially occupy- 

 ing both valves. Foramen of the ventral valve a broad, shallow sinus, which is filled by 

 the prominent cardinal process of the opposite valve, the latter being perforate or 



l For complete bibliography to 1897, see Schuchert, C, IT. S. Geol. Surv., Bull 87 p 24f\ 

 1897. 



