OSTRACODA. 657 
Beyrichia.] ; 
thick, in a ventral view resembling lips; surface of valves gently convex within the 
wide concave border, the central part of the upper half depressed around a narrow 
pit; in front of the pit occasionally a slight rounded elevation. Surface beautifully 
marked with small pits closely arranged in concentric lines, usually less curved than 
the ventral outline of the valves. 
This is one of the prettiest of the numerous Ostracoda occurring in the Trenton 
of Minnesota. It is also one of the most easily recognized, the thick, lip-like edges, 
and the concentric surface markings being unusually distinctive. 
Formation and locality.—Near the top of the Galena shales, Goodhue county, Minnesota. 
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Genus BEYRICHIA, McCoy. 
Beyrichia, McCoy, 1846. Synop. Sil. Foss. Ireland, p. 57. 
Carapace small, equivalved, oblong or semiovate, with a straight dorsal and 
convex ventral outline. Typically each valve has two sulci and three lobes, of which 
the central one is the smallest; the two larger lobes often coalesce ventrally. Surface 
usually marked with pittings, reticulation, papillz or other ornament. 
Type: Beyrichia kledeni McCoy. 
This genus, after Leperditia, is the most important of all the generic groups of 
Paleozoic Ostracoda. Many of the species also, those of the Upper Silurian rocks 
especially, are comparatively large, specimens over 3 mm. in length being not at all 
uncommon. The individuals, moreover, are generally abundant, layers of rock in 
many instances being crowded with, if indeed they are not largely made up of their 
separated valves. ~ 
In the restricted sense in which the genus is here defined, the oldest known 
species is the Minnesota form about to be described.* It is from the middle third of 
the Trenton shales (?Black River group). Of the Trenton proper, B. bella Walcott, 
may belong to the genus, and I have a doubtful species from the Utica horizon at 
Cincinnati, Ohio; but so far we know of no true Beyrichia from the Hudson River or 
Cincinnati group, those referred to the genus from this formation belonging to 
Ctenobolbina, Drepanella, Bollia, Tetradella, Ceratella and Primitia. In the Clinton, 
however, B. lata Hall (Vanuxem)+} is a good species, and from here on to the close 
_of the Carboniferous system the genus is more or less well represented in every 
group of strata. 
* Prof. T. Rupert Jones has described Beyrichia holli from the Minzvian flags of Great Britain (Geol. Mag., n. ser., Dec. 
2, vol. 8, p. 343; 1881). but the affinities of the fossil seem to me as doubtful. 
+Not Bollia lata Jones, 1890; Quart. Jour. Geol. Soc., vol. 46, p. 12, pl. 3, figs. 1, 2,3. The specimens identified by Prof. 
Jones with B. lata are widely different from the typical Clinton form of this species, which is a true Beyrichia, but I 
cannot distinguish them from Bollia symmetrica Hall, sp. 
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