165 



vertical bar, wliicli do not cross the valves ; side view consisting of 

 one large, nearly circular inflation, with two small terminal compart- 

 ments ; punctje fine. 

 Hab. Para River. 



Terpsestoe minima, Bail., nov. sp. 



Small, quadrangular, with slightly undulate ends ; valves divided 

 into three compartments by two transverse bars at each end, and one 

 at the centre, which cross the entire frustide ; valves also marked by 

 two short costse on each side of the central single bar. 



PoLTMYxus, Bail., nov. gen. 



Siliceous, free, simple, bivalve ; in front view quadrangular, with 

 undulate ends. In lateral view circular. Valves composed of curved 

 ridges, appearing in front view like mamillffi, but in lateral view 

 tapering to the depressed and stellate centre ; summits of ridges, 

 armed with minute spines. (?) 



PoLYMYxus coROXALis, L. W. B., nov. sp. 



Frustules large, symmetrical, bivalve ; in front view quadrangular, 

 with mammilated ends ; in lateral view circular. Lateral surfaces 

 of valves elongated into projections, which in front view appear like 

 mamillas, but in oblique view taper down to the depressed and stel- 

 late centre. Summits of the elevations terminated by minute spines on 

 the margin of the shell. Valves and median band minutely punctate. 



Hab. Para River and mouth of Amazon. 



Triceratium Shadboltii, Bail., nov. sp. ? 



Sides concave, in front view constricted beneath the processes ; 

 concave sides decussately punctate. Lateral surfaces bearing distinct 

 rows of short curved seta3, and three long sharp spines near the 

 bases of the processes. 



Difi*ers from TV. contortum, of Shadbolt, in the sides being con- 

 cave instead of straight. 



Hab. San Antonio Bay, Para River. 



Syringidium Americanum, Bail., nov. sp. 



" Frustules minute, punctated ; central portion quadrangular ; 

 valves unequal, one with a quadrate base suddenly contracted, and 

 then tapering into a pyramidal spine terminated by a mucro ; the 

 other valve sub-globose, with two short basal processes, each ending 

 in a spine." Vid. Pritchard's Infusoria, fourth edition, Plate VII. 

 figure 34. 



Hab. Para River and mouth of the Amazon. 



