452 SYSTE]MATIC PALEONTOLOGY 



Description. — " Slicll roimli, with ^liarj) collar stricture. Length of 

 the tAvo joints = l:5, breadth = 1 : 3. Cephalis hemispherical, with 

 small, circular pores and a stout conical horn of twice the length. 

 Thorax campanulate, suhcvlindrical, witli regular circular, quincuncial 

 pores, three to four times as ln"oad as the bars. Mouth scarcely con- 

 stricted, with tArenty-four to thirty vertical, nearly parallel, little curved 

 feet, which are about half a^; long as the shell, broad, lamellar, rect- 

 angular, and in close contact with their edges. 



''Dimensions. — Cephalis 0.025 long, 0.035 broad; thorax 0.12 long, 

 0.1 broad." Haeckel, 1887. 



The single specimen here figured and referred to this species is incom- 

 plete, the feet being entirely missing. There is consequently some 

 doubt as to the identification. But inasmuch as no other known species 

 agrees with the specimen in as many essentials and as the specimen 

 disagrees with this species in no ofiservable characteristic, it is felt that 

 the identification is reasonal)ly sure. 



Occurrence. — Calvert FomiATiox. Popes Creek, Lyons Creek, 

 Breton Bay. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Suborder ACANTHARIA. 



Superfamily ACANTHOMETRA. 

 Family CHIASTOLIDA. 



This family, according to Haeckel's definition, includes all those 

 Radiolaria whose skeleton grows from the center, is organic (made of 

 acanthin), and consists of a variable number of simple radial spines 

 which are grown together in pairs, each pair forming a single diametral 

 spine. Two genera are included by Haeckel, one of which includes 

 those forms with thirty-two and the other those with twenty radial 

 spines. Another form has been discovered which possesses only ten radial 

 (or five diametral) spines. This would seem to add anotiier genus to 

 the family. This form has already been described l)y Ehrenberg as 

 Litliasteriscus radiatus. Other species of Lithasteriscus were described 

 by Ehrenberg which evidently do not l)elong here, so perhaps a new name 



