CATALOGUE OF ECHINIDA. 
51 
2. Plagionotus Desorii. 
Dorsal tubercles ratber fewer, in only five rows, on the hinder 
half of the lateral interambulacral area. 
Plagionotus Desorii, Gray, Ann. & Mag. N. H. 1851. 
Plagionotus pectoralis, Agassiz & Desor , Ann. Sci. Nat. viii. 
1847, 13, vi. t. 16, f. 15. 
Hab. ? 
a. Moderate sized, without spines. 
8. Brissus. 
Shell thin, ovate, convex ; summit excentric, anterior ; am- 
bulacra narrow, sunk in rather deep grooves, the anterior 
lateral pair rather transverse, the hinder pair longitudinal, 
the anterior odd ambulacra on the crown of the shell reduced 
to a very obscure series of very small roundish twin pores ; back 
with nearly uniform small tubercles; peripetalous fasciole very 
sinuous ; subanal fasciole surrounding the subanal disks, with a 
series of small pores on each side, without any lateral fasciole ; 
mouth anterior ; vent large, in the middle of the edge ; ovarial 
plates four, the hinder large and far apart, with the madrepo- 
riform plate between them; ocellar pores placed in front, and 
alternating with the ovarial pores. 
Nuces, Van Phelsum. 
Brissus, Klein; Gray , Ann. Pliil. 1825, 9; Agassiz dc Desor , 
Ann. Sci. Nat viii. 1847, 12, vi. t. 16, f. 9. 
Spatangus, d., Brissus, Blainv. D. S. N. lx. 184. 
* Subanal area heart-shaped, edged by a broad subanal fasciole; 
the disk radiated , striated, with a series of many marginal yores, 
and with a short fasciole, branched up and edging the sides 
of the vent; the hinder part of the peripetalous fasciole slightly 
bent, but not margined to the hinder edge of the hinder ambu- 
lacra : ; spines on the side of the ambulacra larger, elongate. 
— Metalia. 
1. Brissus stern alis. 
Convex; vertex, gibbosus; subanal area heart-shaped and 
radiately striated. 
Echinospatangus, Gualtier, t 109, f. b. b. ; not good ; subanal 
area too round. 
Spatangus sternalis, Lamk. Hist. iii. 326 ; Deslong, K. M. ii. 687 ; 
Desmoul. Echin. 388. 
Brissus sternalis, Agassiz , Prod. 184; Agassiz & Desor, 1. c. 13. 
Hab. Southern Ocean, Peron. 
a. Without spines, broken. - 
b. and c. With and without spines. Mauritius. Presented 
by Lady Frances Cole. 
