Prof. Bailey on some new Fossil Infusoria. 139 



to, if indeed it be not a variety of, that species. Ehrenberg thus 

 describes Z. rhombus : "Large, lorica turgid, viewed laterally 

 rhomboidal and having rounded angles, surface marked with very 

 delicate striae, the back having a smooth central zone." These 

 characters apply pretty well to our species, with the exception 

 that the central zone in ours is quite distinctly striated, with two 

 sets of lines crossing each other at right angles. The shape of 

 the horns is also" somewhat different in our species from those 

 shown in Ehrenberg's figure. The Z. rhombus was discovered 

 by Ehrenberg alive in sea water at Cuxhaven ; our species is 

 very abundant in the fossil state at Petersburg, Va. 



To the genus Zygoceros I now unhesitatingly refer the living 

 species which I detected in Boston harbor, and which I descri- 

 bed by the name of Emersonia elegans. I propose therefore to 

 change this name to that of Zygoceros Emersoni. My Emer- 

 sonia antiqua (fig. 25, PI. II, of Bacillaria) is probably only the 

 young state of Z. rhombus ? abovementioned. The living spe- 

 cies form zigzag chains. 



4. Triceratium spinosum, nob. (fig. 12.) This large and very 

 curious species of Triceratium occurs sparingly at Petersburg, Va. 

 Its lorica is triquetrous, laterally slightly convex, with obtuse an- 

 gles or horns, the surface marked with shagreen-like projections, 

 and bearing four [or more ?] large spines. Fossil with several 

 other species of Triceratium at Petersburg. The figure shows 

 the outline of half of an individual. 



5. Navicula 1 concentrica, nob. I give this provisional name 

 to the bodies represented in figures 13, 14 and 15. When seen 

 laterally they show an elliptical figure, marked with concentric 

 circular spaces, which when seen edgewise are found to bound a 

 series of gradually diminishing step-like projections. Two indi- 

 viduals [?] probably resulting from spontaneous division, are usu- 

 ally found adhering. Fossil at Petersburg and Piscataway. Fig. 

 13 shows an edge view, fig. 14 the side, and fig. 15 an oblique 

 view, with the end to the front. 



6. Dictyocha fibula? (fig. 16.) This occurs in vast abun- 

 dance among the fossil infusoria at Piscataway, Md. It differs 

 from Ehrenberg's D. fibula, by generally having five instead of 

 four cells in the convex rhomboid, but I am satisfied that the 

 number of cells is a very variable character in this genus. 



