660 THE PALEONTOLOGY OF MINNESOTA. 
{Eurychilina recticulata. 
EURYCHILINA RETICULATA Ulrich, and var. INCURVA, 2. var. 
PLATE XLIV, FIGS. 1 and 2. 
Eurychilina reticulata ULRICH, 1889. Contri. to Can. Micro-Pal., pt. 2, p. 52, pl. ix, figs. 9, 9a. 
Not Eurychilina reticulata (Ulrich) Jonxs, 1890, Quart. Jour. Geol. Soc., vol. xlvi, p. 593, pl. xx, figs. 
13a, 130. 
Si1zE.—Without marginal area, length 1.83 mm.; hight 0.9 mm.; thickness 0.5 mm. 
With 3 tt AC ae Facet Seber staan 
Valves, excluding the marginal area, nearly semicircular in outline, straight 
along the dorsal edge, moderately and almost uniformly convex; sulcus deep, extend- 
ing half way across the body, not as wide as in the next species, its outline more 
sharply defined behind and below than on the anterior side; above the sulcus expands 
and becomes very shallow, while at the midlength it is constricted by a rounded 
prominence on the posterior side; surface, except along the dorsal edge, beautifully 
reticulate. Marginal area wide, narrowest posteriorly; on the outer side it is flattened 
or concave, and slopes inwardly, especially at the ends; ventrally the edge rises to 
form a narrow, wavy. free border; surface marked by radial lines, strongest ventrally, 
least distinct anteriorly; at its junction with the body of the valve, a more or less 
elevated, linear ridge is usually present. Internal characters of valves and marginal 
area almost exactly as in the next species (see plate xurv, fig. 3.) 
This fine species is perhaps the most beautiful of all the Paleozoic Ostracoda 
known to me, and when in a good state of preservation it is scarcely possible to 
confound it with any other. Yet, as cited above, Prof. Jones has referred a Devonian 
specimen from the Corniferous chert of New York to the same species. The 
characters of the valve figured by him are preserved in an empty mold, which in 
splitting the rock presented both an inner and an outer cast. Comparing these 
with the Minnesota species, I am obliged to differ wtih Prof. Jones’ determination. 
Indeed, I doubt if they are even congeneric. The ontline of the body of the valve 
is not semicircular in the Devonian species but has that oblique form which is 
commonly distinguished as “leperditoid.” It is also proportionally a little higher, 
the reticulate ornament extends to the dorsal edge, the sulcus is shorter and much 
less defined, being merely a subcentral depression, and there is apparently no 
rounded prominence behind it. Further, the dimensions given by Prof. Jones show 
that his specimen is considerably larger than any Lower Silurian example of EL. 
reticulata so far seen, the length in the latter rarely, if ever, exceeding 2.5 mm., 
while that of the Devonian form is stated to be 3.5 mm. These differences, if no 
others existed, would be sufficient to prove a distinct species. 
But they are not all, since his fig. 135 shows that the border was convex exteriorly 
while it should be flat or concave; and in fig. 18a, representing an impression of the 
