OLIGOCENE ECHINODEBMATA. 175 



Determinative characters. — Test small, ovoid, upper surface high. Apical system very 

 excentric posteriorly. Ambulacra narrow, anterior indistinct in shallow depression and with 

 short petals in shallow groove. Surface covered with very small tubercles. Peripetalous 

 fasciole indistinct. Peristome large. Periproct high on posterior truncation. 



Dimensions. — Length IS millimeters; width 16 millimeters; height 14 millimeters. 



Description. — This small delicate form is different from any other Tertiary species. The 

 test is ovoid, much elevated, the high apex giving a subcorneal appearance to the upper surface. 

 The apex is very excentric posteriorly and the upper surface slopes from it in all directions. 

 The under surface is convex except for the peristomial depression. 



The ambulacra are narrow, the anterior hardly distinguishable on a nearly flush surface 

 which shows a slight depression. The paired ambulacra have short petals in shallow grooves, 

 the posterolateral pair being not half the length of the anterolateral. 



The interambulacra are broad, the upper portions of the paired areas near the apex being 

 gibbous and terminating in short, narrow ridges. The posterior interambulacrum has a pro- 

 nounced truncation, which slopes inward so that the periproct is not visible from above but is 

 from below. 



The fascioles are very narrow and only traces of them can be seen here and there. 



The peristome is large and bilabial. The periproct is quite large, transverse oval, slightly 

 overhung by the projecting interambulacrum. 



The apical system consists of four genital plates, the perforations of which are near together. 



Related forms. — This species is easily distinguished from other species of this genus by its 

 much elevated upper surface, slightly conical at the apex, and its very excentric apex posteriorly. 

 The sharp truncation of the posterior surface is very characteristic. These and other characters 

 distinguish it from A. excentrica, which still lives in the Caribbean Sea and near the coasts of 

 Florida and also from A. clevei of the Miocene of the island of St. Barthelemy. 



Localities. — Georgia (Bouv6) ; near Bainbridge (figured specimen) and 3i miles south of 

 Sasser on Dawson- Albany public road, Georgia; near Gainesville, Fla. 



Geologic horizon. — Lower Ohgocene. 



Collection. — U . S. National Museum (164744); Geological Survey of Georgia. 



Genus SCHIZASTER Agassiz. 



Schizaster floridanus Clark, n. sp. 



Plate LXXXII, figures la-c. 



Determinative characters. — Test rather large, cordiform, high posterior upper surf ace, nearly 

 flat lower surface. Ambulacra in broad, deep grooves, the petals of the paired ambulacra being 

 very pronounced. Posterior truncation prominent with high periproct. Peristome near anterior 

 margin. 



Dimensions. — Length 50 millimeters; width 24.5 millimeters; height 30 millimeters. 



Description. — The species is represented only by forms in which the test has been replaced 

 by silica, obliterating some of the features but admirably preserving others. 



The test is of rather large size, cordiform, with a sloping upper surface which extends up 

 from the depressed anterior margin to the much elevated posterior margin. The lower surface 

 is nearly flat. 



The ambulacra are broad, the anterior ambulacrum being in a broad deep groove which 

 passes over the anterior margin. The paired ambulacra have broad deep petals, the antero- 

 lateral pair being about one and one-half times as long as the posterolateral. 



The interambulacra are wide and are shghtly gibbous near the apex. The posterior area 

 has a sharp ridge reaching to the posterior margin. A pronounced truncation characterizes this 

 area, the slope being actually inward and the periproct being found high on the surface. The 

 peristome is large and near the anterior margin. 



Locality. — Johnsons Sink, Levy County, Fla. 



Geologic horizon. — Vicksburg group, lower Ohgocene. 



Collection. — U. S. National Museum (164655). 



