Naolculacea.'} infusorial animalcules. 431 



with tumid cells ; puucta depressed, rays ratlier prominent, spines 

 solitary on the centre of the upper margin of each area. Diameter 

 l-192nd. Fossil in Bermuda. Habit of Adinoptjchus scnarius, and 

 of HeliopeJta Melius. 



OMrnALOPELTA (?) punctata. — With six rays and septa; radi- 

 ating areoe, all loosely dotted; thi'ee alternate ones rather more 

 prominent ; margin slender, not clearly radiate, spines obsolete. If 

 i\]i ActinopitycJuis? Diameter 1- 720th. Bermuda. 



0. versicolor. — With six septa and rays; all the radiating arose 

 marked by very fine decussating and granular lines, whence it dis- 

 plays various coloui's, changing from brown to red ; rays strong ; 

 umbilicus hexagonal, crystalline ; margin slender, radiate ; spines 

 single, in the centre of the upper margin of each area. Diameter 

 sometimes 1 -252nd. Mostly smaller. Bermuda. 



Genus Pekiptera, (Ehr.) — Lorica simple, compressed, unequally 

 bivalve ; testa covering the valves, simple, continuous and not 

 cellular (areolar) ; one valve tui'gid and naked (unarmed,) the other 

 winged or horned ; horns afhxed to the extreme margin, sometimes 

 branching. Approaches veiy near to Rhizoselenia and Bicladia ; but 

 the former has one exserted median hom, the latter two. From 

 Hercotheca it differs by its compressed form. 



P. Capra. — Smooth, one end with two simple horns, the otlier 

 iinidentate, or imperfectly bidentate (sub-bidentate) ; intermediate 

 part with narrow transverse lines. Diameter 1-1 440th. Virguiia. 



P. Cervus. — Smooth, larger, with long branching frontal horns. 

 Diameter 1-5 76th. Maryland. 



P. clilamidophora. — Smooth, compressed, almost naviciilar ; one 

 valve on the side plane, and extended by a finely -veined membrane ; 

 the other naked, tui'gid at the centre. Length l-2304th. AVidth 

 with the membrane (a compressed tubule) 1- 11 52nd. Bermuda. 



P. tefracladia. — Smooth, compressed, almost navicular; one valve 

 with four equi -distant setaj, branched at the apex; the other simple. 

 Diameter l-1440th; mth setse, l-864th; without setae, resembles 

 AmjjJiora. Bermuda. 



Genus PoROCYCLiA (Ekr.) — Cylindrical, lorica simple, utricular, trun- 

 cate; each utricle spontaneously divisible through its middle, with apcr- 

 tui-es or minute pits on the margin of the smooth disc ; concatenation 



