52 
CATALOGUE OF ECHINIDA. 
** Subanal area oblong , transverse , edged by a distinct subanal 
fasciole , bent in under the vents, without any fasciole extending 
up the side of the vent, with a series of four or five small pores 
up each side ; spines and tubercles subequcd, of the front half of 
the body rather largest; front of fasciole far from vertex , with 
a distinct inflection near anterior lateral ambulacra, and bent 
up nearly to the vertex of the interior ambulacra i area. — Bris- 
sus. 
The species of this section are most difficult to distinguish ; 
they present several variations, which at first sight appear cha- 
racters, as for example: 1. The size and form of the subanal 
disk, as regards itself, as regards its size compared with the 
thoracic disk, and in the position, number, and size of the 
lateral pores. 2. The form and size of the thoracic disk, and 
the position of the centre and its hinder band. 3. The com- 
parative length of the ambulacra with each other, and with 
the size of the shell. 4. The outline of the peripetalous fascia, 
its approach to the centre of the back. 5. The roundness or 
keeled form of the hinder central dorsal line ; but these varia- 
tions do not appear to be permanent in the specimens of the 
same habitat, but this fact requires verification with a larger 
series ; the form of the fasciole is often different on the two 
sides of the same specimens. 
* Anterior part of fasciole single. 
1. Brissus Scillje. 
Shell depressed ; hinder edge vertical (not oblique, as in 
A. carinatus), anterior lateral ambulacra bent forwards. 
Brissus Scillss, Agassiz , Prod.; Agassiz & Desor, 1. c. 13. 
Spatangus ovatus, /3, Lamk. Hist.; Ency. Heth. t. 158, f. 7. 
Spatangus Brissus placenta, Philippi, Erich. Arch. 1845, 
349. 
Hab. Mediterranean. Palermo. 
a. High in middle of back covered with spines. Mediter- 
ranean. Presented by H. Cuming, Esq. 
b. Ovate, moderately rounded, keeled behind. Mediter- 
ranean. Presented by H. Cuming, Esq. 
c. d. Without spines ; ? 
2. Brissus dimidiatus. 
“ High, carinated (like B. carinatus) ; hinder end vertically 
truncated ; the tubercles of the anterior half of the body larger 
than those of the hinder/’ 
Brissus dimidiatus, Agassiz & Desor, 1. c. 13. 
Hab. Canaries, D'Orb. Mus. Paris. 
