188 Tne American Geologist. September, 1897 
atnetei-; shells allied to BarramleoceraH, nearly 2 feet across and frag- 
ments of Isotelus gigas, indicating a length of 20 inches. 
Such general attainment of unusual size seems to the reviewer from 
the consideration of similar phenomena at other horizons, possible only 
on a deeply embayed coast where life conditions have been exposed to 
minimum infringement. j. m. c. 
TJie morphologii of the Graptolitcs has in recent years been the sub- 
ject of much painstaking research. The results have been of great in- 
terest though the much discussed zoological affinities of these extinct 
organisms will hai-dly be regarded as yet determined. 
Some of these late investigations have been largely directed to the de- 
termination of the conformation of the rhabdosome and the character 
of the cells or thecas, and these have, for the most part, been based up- 
on isolated mono- or dipriouidian stipes preserved in their natural ful- 
ness in limestone matrix. Such are largely the studies by Holm, Wi- 
man, notices of which have appeared in this journal: by Jaekel (Zeitschr. 
der deutsch. Geolog. Gesellsch, vol. 41), Perner (Etudes sur les Grap- 
tolites de Boheme, 1894) and Giirich (Zeitschr. d. d. geolog. Gesell. 
vol. 48, 1897). The work of Holm and Wiman has been most resource- 
ful in the adaptation of various mechanical means to the development 
of material and the achievement of the objects sought. While these in- 
vestigations have elucidated the conformation of the rhabdosome, the 
really remarkable discoveries of Ruedeinann pertaining to the morphol- 
ogy of the entire colony in DiplogrdptiiH, as well as their development 
and mode of growth, have been based upon specimens preserved in the 
Utica shale which has been deposited under such conditions of quiet- 
ude as to retain the colony without dismemberment. 
Dr. Ruedemann's preliminary account of these discoveries appeared 
in the American Journal of Science for 1895 (vol. 49), while his com- 
pleter paper, just issued, is in the Fortieth Annual Report of the N. Y. 
state geologist (1897). pp. 219-249, pi's. 1-.5, to which the reader is refer- 
red for a study of the author's remarkable illustrations. The fronds of 
these diprionidians are shown to be umbrella-shaped colonies, the com- 
ponent stipes of which radiating from a central disk, are not of the same 
length, in this unequal length evincing their unequal age. At the center, 
also, either above or below the central disk, is a quadrangular body which 
the author originally intei-preted as a float or pneumatocyst similar to 
that of recent Siphonophora . With later evidence, a different function 
for thi.s organ, now termed the basal cyst, is suggested, namely, a con- 
trivance which secured the stability of the colony in the ooze of its hab- 
itat. Gonangia, which have been suspected and even alleged by other 
authors, are here clearly demonstrated, existing in a single cycle about 
the central disk and it is confidently asserted that the embryo grapto- 
lites. or sicula3, are observable within these gonangial sacks, attached 
by their apices to a central base. The analysis of these fossils demon- 
strates a near relationship between Diplograptus and the Sertularians, 
but upon the possession by the graptolites of the horny sheath in the 
embryo and the horny axis df the rhabdosome, it is proposed to place 
these organisms in a distinct and new class, the Rhabdophora. 
