CATALOGUE OF ECHINIDA. 
59 
Tripylus, Gray, Ann. & Mag. N. H. 1851. 
Tripylus, sp., Philippi, Erich. Arch. 1845, 344 (not character- 
ized). 
Agassizia, sp., Agassiz £) Besor , Ann. JSci. Mat. 1847, 20. 
This genus chiefly differs from Besoria and Schizaster in the 
regular cordate form and central vertex : it differs from Brissi- 
opsis in the absence of the subanal fasciole. 
1. Tripylus excayatus. 
Cordate, suborbicular ; ambulacra oblong, linear: posterior 
lateral pair two-thirds the length of the anterior lateral ones ; 
the sides of the hinder part of the peripetalous fasciole rather 
diverging. 
Tripylus excavatus, Philippi, Erich. Arch. 1845, 342, t. 11, 
f. 1. 
Agassizia excavata, Agassiz & Besor, 1. c. 20. 
Hab. Southern extremity of America. 
a. Covered with spines. South America. Presented by 
Capt. P. Parker King, R.N., 1832. 
2. Tripylus Philippii, t. 5, f. 1. 
Cordate, rather depressed ; lateral ambulacra oblong, linear, 
the hinder pair not half the length of the anterior ones : the 
sides of the hinder part of the peripetalous fasciole parallel. 
Tripylus Philippii, Gray, Ann. § Mag. N. H. 1851. 
Hab. 1 
a. Without spines, broken. S America. Presented by 
Captain P. Parker King, R.N., 1832. 
14 . Schizaster. 
Shell broad, depressed in front, high and narrow behind, with 
the apex very near to the hinder edge ; ambulacra very deep ; 
the front lateral nearly parallel to the odd anterior one, and 
much larger than the hinder ; the odd anterior very broad and 
deep, surrounded by a broad very flexuous peripetalous fas- 
ciole, with a second lateral fasciole separating from it, and 
directed behind, under the vent ; spines of the plastron larger, 
longer, cylindrical, dilated at the end, spade-like ; ovarial pores 
two, rarely three or four, the posterior being the most perma- 
nent ; ocellar pores five. 
Ova, Van Phelsum; Gray, Ann. Phil. 1825. 
Brissoides, Klein. 
