114 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



sized, cordiform, 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 forward, the 

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

 border of the test. 



Locality and geologic occurrence. — Miocene(?), Brazil, Costa Rica, 

 A. Alfaro, collector, U. S. National Museum station No. 5505, two 

 specimens. 



Type.— Cat, No. 324460, U.S.N.M. 



SCHIZASTER PANAMENSIS Jackson. 



Plate 50, figs. 2-3. 



ScMzaster panamensis Jackson, Proc. TJ. S. Nat. Mus., vol. 53, 1917, p. 500 P 

 pi. 66, figs. 2, 3. 



The material consists of an internal mould free from matrix, and 

 three specimens more or less complete, embedded in porous, dark- 

 colored Volcanic tuff which also bears some fragments of lignite. 

 The specimen, free from matrix, is the most completely preserved, 

 although somewhat compressed dorso-ventrally, and is selected as 

 the type. The specimen measures 48 mm. in length, 40 mm. in width, 

 and 25 mm. in height. The petals of the ambulacra are situated in 

 broad, deep furrows. The anterior petal III extends to the anterior 

 limit of the test and measures 23 mm. in length. The paired anterior 

 ambulacra II and IV are in grooves 13 mm. long and diverge widely 

 from the anterior petal. The posterior petals I and V are shorter 

 than the anterior pair, measuring 5 mm. in length, and are directed 

 almost straight backward. The position of the periproct is not 

 clearly indicated on the mould, but apparently it is near the upper 

 part of the posterior face. The peristome is wide and rounded, and 

 is situated 16 mm. from the anterior border of the test. The peri- 



