of Microscopical Organisms. 343 



" Frustnles minute, punctated ; central portion quadran- 

 gular ; valves unequal, one with a quadrate base suddenly 

 contracted, and then tapering into a pyramidal spine, ter- 

 minated by a mucro ; the other valve sub-globose, with 

 two short basal processes, each ending in a spine." 



Hub. Para River, and mouth of Amazon. 



One species of this singular genus, the Si/ring-idiiim 

 Americamini, has been figured in the last edition of Pritch- 

 ard's Infusoria, from figures sent in letters to the authors 

 of that work. The figure there given is much larger than 

 the present ones, and needs no comments. One species at 

 least, however, still remains undescribed, which may be 

 characterized as follows. 



Fig. 65. Syringidium simplex. Bail., nov. sp. Frus- 

 tules minute, punctated ; central portion quadrangular, 

 larger and stouter than in S. Americanum ; valves unequal, 

 both gradually tapering into pyramidal cones, one of which 

 terminates in a mucro, the other in a minute, sharp spine ; 

 valves nearly symmetrical ; no basal processes as in S. 

 Americanum. 



Hab. Para River. 



It will be noticed that Fig. 64, although called S. Amer- 

 icanum above, differs considerably from Figs. 63 and 62. 

 I am not willing, however, to declare them distinct, as 

 they were not originally called by different names. I have 

 found also, from this same locality, another specimen, dif- 

 fering considerably from either of the above, which will be 

 figured on some future occasion. If Fig. 64 should be 

 considered as distinct from S. Americanmn, I would sug- 

 gest the name of " uccidenlale" which was originally given 

 to all three of these forms. 



Figs. 66-68. Zygoceros occidentalis. Bail., nov. sp.? 



Fig. 69. Denticella trinacria, Bail., nov. sp. ? 



I have already spoken of these forms, regarding them as 

 varieties of Zi/goceros Mobilicnsis, B. 



