OSTRACODA. 681 
Moorea. ] 
among Ohio and Manitoba specimens, the ventral connection between the inner and 
marginal ridges is obsolete. 
The Minnesota specimens, although from a much lower horizon than the types, 
cannot be distinguished from them even as a good variety. 
Formation and locality—Galena shales (Nematopora beds), near Canuon Falls, Minnesota; upper 
beds of the Cincinnati or Hudson River formation at Oxford, Ohio, and Stony Mountain, Manitoba. 
Genus MOOREA, Jones and Kirkby. 
Moorea, JONES and Kirksey, 1867. Quart. Jour. Geol. Soc., vel. xxiii, p. 494; 1869, Ann. Mag. Nat. 
Hist., ser. 4, vol. iii, p. 225, and 1886, ser. 5, vol. xviii, p. 261; 1887, Proc. 
Geol. Assoc., vol. ix, p. 508. 
Carapace very small, more or less oblong or ovate, with the valves compressed, 
rather thick shelled, smooth, punctate or granulose, and bounded by a raised 
marginal ridge; the ridge may be developed only at each end, or it may continue 
all around. Within the marginal ridge, the flat or gently convex surface shows no 
trace of a sulcus, pit, nor of lobes. 
Types: M. obesa and M. tenuis Jones and Kirkby. 
This genus is now for the first time recognized in Lower Silurian rocks, and 
two of the species to be described fairly illustrate the characters of the genus. The 
third, M. ? perplexa, is of doubtful affinities. A fourth species, M. smithii, has been 
described by Prof. T. Rupert Jones from the Wenlock. This seems to bea question- 
able Moorea, the carapace being too convex and blunt at the ends, while the ridge, 
which should be submarginal, is here central and bifurcated posteriorly. A fifth 
species, M. kirkbyi, described from the Corniferous limestone of Ontario by the same 
author, is not far removed from M. angularis, while in the sixth M. bicornuta Ulrich, 
from the Hamilton, the anterior end bears two spines. WM. granosa Ulrich, from the 
Chester group of Kentucky, is peculiar in having a granulose marginal ridge and a 
rounded subcentral spot outlined by a row of minute papille. The original types 
are from the Carboniferous rocks of southern England. 
All these species are distinguished from Kirkbya, Jones, certain species of which 
they greatly resembly, by the absence of a central pit. Somealso resemble Placentula 
Jones and Holl, and certain species of Bollia, but the first of these genera has a small 
dorsal loop and sulcus, while the latter always has a horseshoe-shaped ridge of which 
no trace is to be observed in Moorea. The valves in the new genus Macronotella are 
more convex and without the marginal ridge. 
