284 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



Genus BEYRICHIA McCoy, emended. 



Beyrichia McCoy, Synop. Sil. Foss. Ireland, 1S46, p. 57. 



Beyrichia Bell and Forbes, in Burineister's Org. Tril., London, Suppl. App., 



p. 124. 

 Beyrichia McCoy, Brit. Pal. Rocks and Foss., 1854, p. 135. 

 Beyrichia (part) Jones, Ann. and Mag. Nat. Hist. (2), XVI, 1S55, p. 85. 

 Beyrichia (part) Hall. Nat. Hist. New York, Pal., Ill, 1859 [1861], p. 377. 

 Beyrichia (part) Barrande, Syst. Sil. dn Centre Boheme, I, Suppl.. 1S72, p. 490. 

 Beyrichia (part) Zittel, Handbuch d. Pal., II, 1885, p. 553. 

 Beyrichia Belter, Zeits. d. d. geol. Gesell., XXXVII, 1SS5, p. 628. 

 Beyrichia (part) Jones and Hole, Ann. and Mag. Nat. Hist, if.), XVII, 1S86, 



pp. 338, 315. 

 Beyrichia Jones and Kirkby. Proc. Geol. Assoc, IX, 1SSG, p. 505. 

 Bollia (part) Jones, Ann. and Mag. Nat. Hist. (5), XIX, 1887, p. 40S. 

 Beyrichia Yerworn, Zeits. d. d. geol. Gesell., XXXIX. 1SS7, p. 27. 

 Beyrichia (part) Krause, Zeits. d. d. geol. Gesell., XLI, 1SS9, p. 17. 

 Bollia (part) Krause, Zeits. d. d. geol. Gesell., XLI, 1889, pp. 13, 14. 

 Beyrichia Miller, North Amer. Geol. and Pal., 1SS9, p. 534. 

 Beyrichia Vogdes, Annals New York Acad. Sci., V, 18S9, p. 8. 

 Gtenobolbina (part) Uleich, Jour. Cincinnati Soc. Nat. Hist., XIII, 1890, p. 111. 

 Strepula (part) Krause, Zeits. d. d. geol. Gesell., XLIII, 1891, p. 498. 

 Beyrichia (part) Ulbich, Geol. and Nat. Hist. Surv. Minnesota, Final Rept., 



Ill, PI. -1. 1894, i). 657. 

 Beyrichia Koken, Die Leitt'ossilien, 1896, p. 40. 

 Beyrichia Gueich, Verb., d. Russ.-Kais. Mineral (iesell. zu St. Petersburg (2), 



1896, p. 385. 

 Beyrichia Geabau, Bull. Buffalo Soc. Nat. Sci., VI, 1899, p. 306. 

 Beyrichia Ulbich and Bassleb, Proc. V. S. Nat. Mus., NXX. 1906, p. 151. 



Carapace comparatively large, 2 mm. to 5 mm. in length, semiovate 

 or semicircular to oblong in outline, with sharp dorsal and rounded 

 ventral angles. Valves only moderately convex, strongly impressed 

 with two vertical furrows, extending from the straight dorsal edge 

 to the ventral portion of the valve so as to divide the intramarginal 

 part of the surface into three unequal and unsymmetrical lobes. 

 These vary considerably in size with respect to each other and with 

 respect to their separation; also in the development of their ventral 

 ends. The furrows may be much narrower or they may equal the 

 ridges in width. The ovate median lobe is the most constant in form 

 and size, usually the smallest, and ordinarily begins some distance 

 beneath the dorsal edge. The anterior lobe, though generally the 

 largest, is the most variable in size and form, being also often broken 

 up into subsidiary nodes. The posterior ridge is, as a rule, the nar- 

 rowest, runs nearly parallel with the posterior border, is rounded 

 and thickest above, sometimes constricted near its middle 1 , and often 

 tapers to the vanishing point near the middle of the ventral edge. 

 In other species it joins the ventral prolongation of the anterior lobe, 

 in which cases commonly all three lobes are joined. When only two 

 of the lobes are connected, it is. perhaps invariably, the median and 

 the anterior. Ventral pouch (presumably of female) egg-shuped or 



