228 M.A. Pomel on the Classification of Echinida. 
less types. Some have the anus far from the apex; the 
peristome is small and but slightly angular in Echinoconus ; 
it is large and strongly notched in Pygaster; others have the 
frame of the periprocta partly constituted by the genital circle— 
Echinoclypus ; and as the peristome is strongly notched, there 
is a manifest passage to the type of the regular Echinida. 
The Globiform EKchinida are very homogeneous, but yet 
they can be divided into two distinct subfamilies, the Cida- 
rida, with the ambulacra prolonged on the buccal membrane, 
and destitute of buccal branchie, and the Hchinida, with the 
ambulacra not prolonged, but provided with buccal branchie, 
applied against the frame of the peristome in a more or less 
deep notch. 
The Cidarides are only varied in a slight degree; some 
have the ambulacra flexuous—7Zemnocidaris and Cidaris. 
Others have the ambulacra straight, and the tubercles rela- 
tively small—Orthocidaris and Diplocidaris. 
The Echinides are, of all the Echinida, those in which the 
serial arrangement is most difficult to find. We have decided 
to make two groups of them, the perforation of the mamilla 
of the tubercles being characteristic of the Diademia and 
wanting in the Echinia. 
The Salenia have been raised into a tribe, and even into 
a family, because one of the pieces which, in the ordinary 
Echinida invest the anal membrane, is in this case fixed to 
the test, and also because the anus is eccentric in the peri- 
proctal frame, as is the case in many other living types. It 
is therefore probable that this tribe will be suppressed, or 
perhaps be distributed among the others. 
The Diademia include several types; Heterocidaris, with 
short ambulacral lips and a small peristome; Hemicrdaris, 
with a large, diagonal peristome, and with very narrow am- 
bulacra ; Diadema differing from these by its tubercles being 
equal in the two areas; and Pedina with a small peristome, 
much notched, and with slightly developed tubercles. 
The Hchinia are a little more varied; the peristome has 
its lips but slightly unequal, and its notches sharp in 
some; the test has no sculpture, and the tubercles of the two 
areas are unequal in AWropeltis, subequal in Phymasoma and 
Celopleurus ; the test is ornamented with sculpture and im- 
pressions in Temnoplewrus and Salmacis. The peristome has 
no notches, or very slight ones, and the lips are very unequal 
in Codechinus, equal in Psammechinus. Its notches are very 
clean, and even deep, and the lips very unequal, in Magnosia 
and Stomechinus. 'The peristome is almost round, and the 
notches are narrow and deep in Tripneustes. Lastly, with 
