Naviciilacm.^ infusorial animalcules. 443 



SYMBOLOpnoRA (?) Tcfras. — Tiivgid; valves with very fine dotted 

 rays ; umbilicus stellate, smooth, crucial, or with four slender rays. 

 Diameter 1 -432nd. Soxithern Ocean. 



S. (?) Penfas. — Turgid; disc with very fine dotted rays; umbi- 

 licus smooth, stellate, with five narrow rays. Diameter 1- 432nd. 

 Southern Ocean. 



S. (?) Hexas. — Testulc turgid; disc like that of the preceding, 

 but the stellate umbilicus with six slender rays. Diameter 1 -432nd. 

 Southern Ocean. 



Genus Syndendrium. (Ehr.) — Lorica bivalve, not concatenate ; sub- 

 quadrangular, with no central umbilicus ; one-ceUed ; valves unequal, 

 rather turgid ; one smooth, the other with numerous styles or corniculi 

 branched at the apex, and distributed upon the flat centre of the 

 valve, the margin being bare. This differs from the nearly-allied 

 genus Di'cladia, by the valve having not merely two but many 

 styles. 



S. Diadema. — Testules lanceolate ; 5 to 6 spines in the centre of one 

 valve, forked or pencillate (split up in a brush-like manner) their 

 length equalling the thickness of the testa. Diameter l-1152nd. 

 In Peruvian Guano. 



Genus Svstephakia. (Ehr. ) — Lorica orbicular, bivalve, concatenate ? 

 Testa of valves cellular iareolate) not radiated, nor divided by septa ; 

 with an external cii'clet of spines, or an erect membrane, on the 

 central portion (disc) of each valve ; not on the margin. Has the 

 habit of a Coscinodiscus (as of C. Ihuatus), but the cii'clet of spines 

 unites the adjoining corpuscles during spontaneous fission, and in the 

 young state. Thus Systephania differs from Coscinodiscus, as Denti- 

 cella differs from BiddulpMa. 



S. aculeata. — Valves loosely cellular ; cells disposed in parallel 

 rows, 8 in 1-11 52nd ; aculei not dense, 12 placed on the disc, but near 

 the margin. Diameter l-324th. Bermuda. 



S. Corona. — Yalves more densely cellular, and in parallel rows, 12 

 in 1-1 152nd ; with 48 erect aculei, closely set and near the margin. 

 Diameter 1-3 4 8th. Bermuda. 



S. Biadema. — Yalves densely cellular ; cells in parallel rows, 14 

 in ] -1152nd, aculei bent inwards, marginal, conjoined at their extre- 



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