1886. ] Geology and Paleontology. 157 
cies occurs in the Upper Trias, six in the Upper Lias, thirty-nine 
from the other Jurassic beds, eleven from the Purbeck and 
Wealden beds, three from the green sand, and six from the 
ocene. 
Silurian—Dr. O. Hermann (Geol. Mag. Sept., Oct., 1885) 
gives an account of the organization of the Graptolithide. The 
entire polypidom proceeds from a simple hollow cone called the 
sicula. In the external wall of this dagger-shaped organ a single 
or double solid axis is developed. Thus, until the sicula is found, 
it is impossible to tell whether any given form belongs to the 
monograptide or to a two-branched family. Sprouting does not 
always commence at the same spot of the sicula. It is now 
assumed that all graptolites provided with a sicula were not 
attached bodies, the character of the termination, and its disap- 
pearance in full-grown individuals, militating against attachment. 
In some of the much-branched Dichograptidz a central chitinous 
disc unites the basal part of the branches. It has been ascertained 
by Hopkinson that in some graptolites the hydrothecze were 
separated from the coenosarc by a well-marked septum, and that 
the ccenosare was divided by septa into transverse joints. The 
oldest graptolite, according to Brogger and Hermann, is Dictyo- 
grapius teneilus; and the family Dichograptide, which includes 
complicated and elegant forms of graptolites, is older than the 
universal groups. This family appears in the Lower Silurian 
(Waring), becoming extinguished before the Upper Silurian is 
reached. The Phyllograptidze and Lasiograptidz seem to be con- 
: fined to the lowest division of the Lower Silurian, the Leptograp- 
tide and Dicranograptide to the Lower Silurian, while the 
Diptograptidz and Retiohtes commence in the lowest Lower 
Silurian, but are most developed at its upper boundary, and 
extend into the Upper Silurian. The simplest family, the Mono- 
graptidæ, are, according to Lapworth, strictly confined to the 
Upper Silurian. The genus Dictyograptus, of which Tullberg 
makes a new family (though Hermann ranges it with the Dicho- 
graptidæ), maintains itself through the entire Silurian, and passes 
into the Devonian. 
Devonian.—Professor Williams has described (Geol. Mag.,Sept., 
1885), Prestwichia eriensis, a new Limuloid from the Devonian 
of Le Bouf, Erie county, Pa. 
enland. The second or Mill creek series corresponds closely 
to the Dakota, and seems to represent the flora of the Cenoma- 
