(')F DENISON UNIVERSITY. 
55 
In connection with this genus it is necessary to notice the 
only exception to the statement that no species of Phillipsia is known 
below the Waverly. P. longicaudata, H. described as from the Ham- 
ilton though some doubt was expressed whether it was not after all a 
coal-measure species, is certainly a Phillipsia and, judging from the 
figure, identical even in the state of preservation with P. sartgamonen- 
sis, M. and W. It seems quite likely that the same specimen was em- 
ployed in both figures, though it was derived from an unknown local- 
ity north-east of Des Moines, Iowa. 
The genus Phillipsia proper, begins at the beginning of Division 
III, i. e., at that horizon which most nearly corresponds with the low- 
er part of the' Burlington group, and forms the introductory member 
of the Carboniferous in Ohio. 
Genus Proetus. 
The Devonian of America is well supplied with species of this 
genus, of which five species are found in the upper Helderberg. The 
corniferous limestone contains P. folliceps^ P. clams, P. canal tea latus, 
P. verneiiili, P. tnicrogemma, P. (?) planimarginalus, P. sienopyge, P. 
ovifrons, P. delphinulits and P. tiimidiis — ten species. In the Hamil- 
ton Prof. Hall notes, P. haldemani, P. macrocephalus, P. rowi, P. jeju- 
nu,s P. phocion, P. proiiti, P. nevadee, P occidens. 
Then, strangely enough, the race seems to end So far as evidence 
thus far has offered, trilobites ceased to exist with the end of the Ham- 
ilton, as no remains are known from the Portage and Chemung strata. 
This has naturally given much trouble to geologists in view of the con- 
siderable development of these Crustacea in the Carboniferous. The 
whole difficutty disappears when the view here advocated is accepted 
and we find in Ohio a continuous sequence from Hamilton to Coal- 
measures with no serious break. The Hamilton genera are very grad- 
ually superceeded in the lower Waverly and the transition to the coal- 
measure species is complete. 
PROETUS (?) (cf HALDEMANI. H.) 
(Plate I, Fig. 12) 
Our material is too poor to permit a rigid definition of the species, 
but its position is so near the base of the Waverly that its peculiarities 
may warrant a reference. 
