1896.] Geology and Paleontology. 581 
through a Rhoéchinus stage, and later a Paleechinus stage. Melonites 
in its development passes through an Oligoporus stage. 
An early stage in developing Echinoderms was named the “ pro- 
techinus” stage, At this stage are first acquired those features which 
characterize the developing animal as a member of the Echinoidea. 
The protechinus stage in Echinoderms is directly comparable to the 
protoconch of Cephalous Mollusca, the protegulum of Brachiopods, the 
protaspis of Trilobites, ete. The Echinoderm at this period in its 
growth has a single interambulacral plate (representing a single column 
of such plates), and two columns of ambulacral plates in each of the 
five areas. This stage is seen in Oligoporus, Lepidechinus, Goniocidaris 
and other genera ; it finds its representative in an adult ancestral form, 
in the primitive, oldest known genus of the class Bothriocidar is of the 
Lower Silurian, which has but one column of interambulacral and two 
columns of ambulacral plates in each area. 
Species of Oligoporus and Melonites with few interambulacral 
columns are considered the more primitive types, as they are repre- 
sented by stages in the development of those species which acquire a 
higher number of columns in the adult. 
The structure of the ventral border of the corona of Archzocidaris 
was described. It presents a row of plates partially resorbed by the 
encroachment of the peristome, as in modern Cidaris, ete. Ambulacral 
and interambulacral plates on the peristome were described in Archzeo- 
cidaris, also teeth and secondary spines on the interambulacral plates 
of the corona. 
This paper contains a classification of Palseozoic Echini based on the 
structure and development of the ambulacral and interambulacral areas 
and the peristome. It will be published in the Bulletin of the Geolog- 
ical Society of America.—Science, Nov. 22, 1895. 
American Fossil Cockroaches.'—This memoir, published as 
Bulletin 124 of the U. S. Geological Survey, is a revision of the known 
species of American fossil cockroaches to date. The descriptions of — 
new forms are interpolated in a systematic list of all the species yet 
recovered from the rocks, and such tables have been added as may en- 
able the student to readily determine any new material. With the 
publication of this essay all species hitherto described will have been 
figured. 
RP; Bulletin of the United States Geological Survey, No. 124. Revision of the 
American Fossil Cockroaches, with Descriptions of New Forms, By Samuel H. 
Scudder, Washingtou, 1895. 
. 
