62 
PATAGONIAN EXPEDITIONS : PALEONTOLOGY. 
Fam. SPA TANGIBLE Ag. 
Gen. SCHIZASTER Ag. 
2. Schizaster ameghinoi v. Ihering. 
PI. XIII, Fig. i"- 6 . 
1897 Schizaster ameghinoi v. Ihering, in: Rev. Mus. Paul., v. 2, p. 338. 
Test moderately depressed (our specimens have suffered from pressure 
and are distorted in different directions), highest in the posterior part, 
back of the apical system, where it is raised to a distinct longitudinal 
carina between the posterior ambulacra. Outline cordiform, with a deep 
notch anteriorly. Apex situated back of the middle of the upper surface. 
Anus in the upper part of the truncated and vertical posterior extremity. 
The anterior ambulacrum in a deep groove, the margins of which are 
quite distinct, but rounded, and run almost parallel toward the anterior 
edge of the test. The sides of the groove are oblique and concave. 
Pores of the anterior ambulacrum regular, those of each pair separated 
by tubercles, which form two rows in the groove. Anterior and posterior 
lateral ambulacra distinctly sunken ; the two anterior curved, first running 
close to the anterior ambulacrum, then diverging. Posterior lateral ambu- 
lacra very short, hardly one-third as long as the anterior lateral ones. 
Peripetalous fasciole forming a sharp, almost rectangular, re-entering angle 
in the posterior lateral interambulacral space, and forming also a re-enter- 
ing angle in the anterior lateral interambulacral space. 
Length, 56 mm ; width, 5 1 mm ; height, 29 mm ; but growing much 
larger as indicated by fragments. 
Remarks : The description given by v. Ihering is entirely insufficient to 
recognize this species ; but since no other species of the genus is known 
from Patagonia, it is perfectly safe to assume that we have to deal with 
this species. 
Record of specimens: Mouth of Santa Cruz River, 2 sp. ; Paso del Rio 
Santa Cruz, 3 sp.; San Julian, Oven Point, fragments of 2 specimens, 
imbedded in matrix. 
Distribution : Gulf of San Jorge (v. Ih.). 
Affinities: Micr aster atacamensis and valdimanus of Philippi (1887, p. 
231, pi. 52, f. 2, 3), the first from the Pliocene Coquimbo beds of Chile, 
the second from the Navidad beds, belong apparently to Schizaster. S. 
