220 MESOZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



The apical system is central, coincident with the apex, about on a level with the highest 

 portions of the ambulacral petals. The specimen is too weathered to jDermit of making out 

 the details. 



The peristome is large, subpentagonal, central, at the deepest point of the concavity on the 

 under surface. The ambulacral furrows are simple, straight shallow grooves extending from 

 the peristome nearly to the margin. 



The periproct is large, circular, inframarginal, almost marginal. 



Dimensions. — Length 134 millimeters; width 116 millimeters; height 50 millimeters. 



Related jorms. — It is unnecessary to discuss here the related recent forms. The nearest 

 fossil form is Diplothecanthus dalli, which is to be distinguished by being relatively higher, in 

 having the apex slightly excentric posteriorly and angular, with a straighter slope anteriorly 

 and a steeper slope posteriorly, in having the apical system sloping downward anteriorly, and 

 in having the interporiferous areas more tumid and coalescing around the madreporite. 



Locality. — Near Labelle Landing, Caloosahatchee River, Fla. 



Geologic horizon. — Pliocene (?). 



Collection. — U. S. National Museum (165693). 



Order ATELOSTOMATA. 



Suborder ASTERNATA. 



Family CASSIDULID.E. 



Genus CASSIDTJLUS Lamarck. 

 Cassidulus berryi Twitchell, n. sp. 



Plate CI, figures 3a-d. 



Determinative characters. — Test small, subcircular in marginal outline; upper surface much 

 depressed, convex; sides and ends equally and gently declining; margin angular, posterior end 

 rostrated; under surface concave, more so anteriorly around the peristome. Apex central; 

 apical system excentric anteriorly. Ambulacral areas rather broad in petaloidal dorsal portions, 

 very narrow above the margin. Peristome small, anteriorly excentric, pentagonal, with a 

 flosceUe. Periproct oval, supramarginal, in a short, shallow sulcus. 



Dimensions. — Length 2S millimeters; width 27 millimeters; height 11 millimeters. 



Description. — The only specimen of this species so far reported was found recently in North 

 Carolina by E. W. Berry, of Johns Hopkins Universitj 7 , in whose honor the species is named. 

 Unfortunately, the specimen is damaged, so that a number of important details can not be made 

 out; but the characters which can be made out prove it to be distinct from the other American 

 representatives of the genus. The test is small, about an inch in diameter; subcircular in 

 marginal outline, the longitudinal diameter slightly exceeding the transverse. The upper sur- 

 face is much depressed, convex, sides and ends equally and gently declining; margin rather 

 sharply angular all around; posterior end rostrated and faintly notched beneath the periproct; 

 under surface concave, more so anteriorly around the peristome than elsewhere. The apex 

 is central. 



The ambulacral areas are rather broad in the petaloid dorsal portions, very narrow above 

 the margin and actinally; the petals are rather broad, subelliptieal, subequal in length, nearly 

 closing at the ends. The details are obscure. 



The apical system is excentric anteriorly. The details can not be made out on the specimen. 



The peristome is small, anteriorly excentric, beneath the apical system, pentagonal, with a 

 floscelle having prominent bourrelets. 



The periproct is oval, longitudinally elongate, supramarginal, in a short, rather wide, shal- 

 low sulcus, which extends to and faintly notches the posterior margin. 



