62 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 78 



EREMOS BRYOGRAPTORUM Westergaard 



Plate 8, Figure 32 



Eremos bryograptorum (Westergaard, Mss.) Mobekg and Segerberg, Medde- 

 lande Fran Lunds Geologiska Faltklubb, ser. B., No. 2, 1906, p. 75, pi. 3, 

 fig>24. 



Our knowledge of the species is based upon the original illustration 

 reproduced on Plate 8. 



Occurrence. — Canadian {Bryograptus beds) : Fogelsang, Sweden. 



Genus HIPPONICHARION Matthew 



Hipponicharion Matthew, Trans. Royal Soc. Canada, vol. 3, sec. 4, 1886, p. 64. — 

 Miller, North Amer. Geol. and Pal., 1889, p. 549; Trans. New York Acad. 

 Sci., vol. 14, 1895, p. 132. 



Genotype. — Hipponicharion eos Matthew. 



Matthew describes three species of this genus, namely, Hipponi- 

 charion eos, H. cavatum, and H. minus. While obviously closely 

 related, the forms are j^et distinguishable. As to the genus, it is a 

 well-marked stage in the development of these peculiar crustaceans. 

 The family relationship to Beyrichona is evident enough in the general 

 shape of the valves, in the mid-dorsal depression, and in the dis- 

 position of the surface ridges and nodes. The generic peculiarity of 

 Hipponicharion lies in the greater distinctness of the lateral ridges, 

 these extending as sharply defined elevations from the cardinal angles, 

 to a point near the middle of the ventral border. The ventral ex- 

 tremities of these submarginal ridges, v^^hile more or less closely 

 approximated, still remain sharply separate in Matthew's three 

 species, but in H. matthewi Wiman, and even more so in the new 

 H. conjiuens, the gap is closed. Aside from the ridges, the surface 

 of the valves is depressed ; in H. eos and H. minus flat ; in H. cavatum, 

 rather strongly concave. A node or thin curved ridge occurs a little 

 in front of the middle of the dorsal half of each valve. This node, 

 though recognizable in Beyrichona, is much better developed in 

 Hipponicharion. It is not possible with the material at hand to- 

 determine whether the edges of the two valves are perfectly equal 

 or overlap. If overlap occurs, it is certainly only to a ver}'- limited 

 extent. A feature of H. cacatum, apparently not observed by Mat« 

 thew, is a narrow transversly lined marginal frill. No sign of such 

 a frill was observed on the other two species, though the specimens 

 of these are full}'' as well preserved. 



fflPPONICHARION EOS Matthew 



Plate 7, Figure 31 



Hipponicharion eos Matthew, Trans. Roj'al Soc. Canada, vol. 3, sec. 4, 1886, p. 

 64, pi. 6, figs. 19, 19o, b; Trans. New York Acad. Sci., vol. 14, 1895, p. 132. 

 pi. 7, figs, la, c. 



