No. 2218. FOSSIL ECHINI OF PANAMA CANAL ZONE-^ACKSON. 499 



the apical system beyond which an elevated sharp ridge continues to 

 the truncated posterior margin. Length, 59 mm.; width, 50 mm.; 

 height, 25 mm. The ambulacra are broad and the odd anterior 

 ambulacral petal III is situated in a deep groove that indents the 

 anterior margin. The two lateral anterior ambulacra II and IV are 

 in deep, broad grooves, with petals 18 mm. long. The posterior 

 ambulacra I and V, similar but shorter, are 9 mm. long. Pcripetalous 

 fasciole is broad and distinct. Interambulacra gibbous, the posterior 

 No. 5 being built up into an elevated keel. The peristome is indis- 

 tinct in our specimen, but as shown in W. B. Clark's excellent figures, 

 is ^vide and near the anterior margin. The periproct is high on the 

 truncated posterior end. 



The type material described by Clark is ascribed to the upper 

 (Jackson) Eocene of Choctaw County, Alabama. 



Locality and geologic occurrence. — Eocene, Bonilla, Costa Rica, Hill 

 collection, U. S. Nat. Mus. Cat. No. 135214, one specimen. 



SCHIZASTER CRISTATUS. new species. 



Plate 68, figs. 2-4. 



The material of this species consists of two internal moulds; as the 

 plates are entirely wanting, of course external characters can not be 

 given. The more perfect of the two specimens measures 40 mm. in 

 length, 36 mm. in width, and 22 mm. in height. Test is moderate 

 sized, cordifomi, sloping gradually from the anterior border up to the 

 median crest, the widest portion being through the middle of the test. 

 The most striking feature of this species is the median keel-like crest 

 that rises sharply from the summit of interambulacrum 5 at the pos- 

 terior border of the test. 



The petal of ambulacrum III is sunken in a deep, wide groove, ex- 

 tending to the anterior border of the test and measuring 23 mm. in 

 length. The petals of the lateral anterior ambulacra II and IV are 

 in deep grooves measuring 13 mm. in length and having about 22 

 plates in each half ambulacrum, as is indicated by the casts of the 

 pores. The petals of the posterior ambulacra I and V are widely 

 divergent from the anterior pair, nearly parallel and directed back- 

 ward in deep, sunken grooves. The grooves are 7 mm. long, and 

 there are about 14 plates in each half ambulacrum at this point, as 

 indicated by casts of the pores. The periproct is situated on the 

 posterior face and coincides with the base of the crest in interam- 

 bulacrum 5. The peristome is wide and situated far forw^ard, the 

 tip which almost closes the mouth being 10 mm. from the anterior 

 border of the test. 



Locality and geologic occurrence. — Upper Oligoceno or Miocene, 

 Brazil, Costa Kica, A. Alfaro, collector, U. S. National Museum sta- 

 tion No. 5505, two specimens. 



Type.—CsX. No. 3244G0, U.S.N.M. 



