21 
Klein, Act Gedan. n. Tab. v. Fig. 14 and 15, as well as by the authors 
just mentioned. 
The second genus of this section is Discoides, the only species of 
which is subuciclus, and is only known as a fossil. The surface of this 
is divided in the same way as the former species. The periphery is 
circular. The vertex is much more depressed, and the base rather 
more concave. One of this species is represented Plate II. Fig. 7- 
Another genus is here introduced by Phelsum, and named by him 
Echinoneus. It agrees, in every respect, with E. Discoides of 
Linnaeus, except in its periphery, which is rather ovate, and not 
angular. It has the same number of areas and ambulacra ; the latter 
being biporous, and having the pores more distant from each other 
than in the preceding genus. 
The second section of the class of Catocysti is Cassis (helmet- 
stone.) These echinites are distinguished by an oval base, from which 
the shell rises in a vaulted helmet-like form. One extremity of the 
oval, that in which the vent is placed, is commonly more produced 
and acute than the other. Klein divided these echinites according to 
their size, into two genera, galece and galeolce ; but Leske, considering 
the difference of size as not sufficient to affect the genus, has very 
properly included them both under the genus echinocorys. As the 
echini of this extensive genus are only found fossil, the changes 
which they have sustained from various kinds of injuries, prevent, in 
many instances, their species being exactly determined. 
The first species, Echinocorys scutatus, Tab. xv. a. b. Kleinii, is 
in general as high as it is long. It has, like most others, five large and 
five small area?, separated by biporous ambulacra. Minute tubercula 
and granulae exist on some parts of the surface, and particularly on 
the base and near to the mouth. The base, the circumference of 
which is nearly elliptical, is almost flat : the edge, however, is slightly 
rounded; and, in its middle, a prominent slip extends from the 
mouth to the anus, near to which, on each side, two bands of minute 
