Revision of Bryozoan Genera.—Cumings. 213 
not merely with a genus in the ordinary sense, but with a true 
genetic line. The only species found below the Cincinnati 
group are D. trentonensis and D, praenuntia* and its varities. 
The latter may for all practical purposes be regarded as the 
western representative of D. ulrichi of the Utica beds of the 
Cincinnati region. 
In the case of Dekayia ulrichi, I believe we are dealing with 
an incipient genus. This species has a considerable range 
and distribution and is highly variable. It varies from strictly 
ramose to strictly frondescent (var. /obata); from perfectly 
smooth to monticulose (D, robusta) ; from very small and del- 
icate (D. obscura), to robust and submassive (D. robusta). 
In internal structure the zocecia may be thick-walled or 
comparatively thin-walled; mesopores are usually numerous, 
but may be considerably reduced in number. The tabulation 
varies but little, and the wall structure is always essentially 
the same. 
I have shown that the smooth type of Dekayia ulrichi pro- 
duces in the Lorraine a truly frondescent form. The monti- 
culose type (D. ulrichi-robusta) also produces a frondescent 
form that ranges throughout the Lorraine. This is the D. 
ulrichi-expansat of the above list. 
Both Dekayia ulrichi-lobata and D. ulrichi-expansa are so 
connected by intermediate forms with D. ulrichi that there can 
be no possible doubt of their direct descent from that species. 
With Dekayia perfrondosa the case is not so simple. The 
possible ancestors of this form are D. ulrichi-robusta, through 
D. subfrondosa; D, solitaria, and a small subramose form oc- 
curring in association with D. ulrichi-robusta, D. ulrichi and 
Callopora nodulosa, in the upper Utica beds, of which I have 
but a single specimen. The latter is very probably but a va- 
riety of D. ulrichi in which the mesopores and acanthopores are 
reduced to a minimum,t D. solitaria seems to belong to the 
same type as D. subfrondosa. The latter is undoubtedly the 
*See Mr. ULRICH’s Observations on the probable relation of this species to 
Dekayia and Heterotrypa, Geol. Minn., iii, p. 273 and footnote, 
+Dekayia ulrichi-expansa n. var (pl. ix, figs. 5, 6; pl. xi, fig. 7) has precisely 
the same internal structure as D, ulrichi-robusta (pl ix, fig. 4; pl. x, fig 2). It 
has, however, an undulating irregularly frondescent or submassive zoarium 
growing from a stout cylindrical base, The surtace ornamentation is the 
same asin D, wirlchi-robusta, with which the variety is connected by every 
gradation. 
tSections of this form closely resemble such sections as figs.15 and 16 pl.ix 
