62 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 



Fam. SPATANGIDA1 Ag. 



Gen. SCHIZASTER Ag. 

 2. SCHIZASTER AMEGHINOI v. Ihering. 



PI. XIII, Fig. !. 

 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, 51 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: Micraster 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. 



