of Microscopical Orfranisms. 333 



of this species in the surface-water of the Para, and have 

 always found them armed with spines at the margin. In 

 some cases these spines are considerably longer than 

 represented in the figure. The parallel puncta are very 

 distinct. 



Fig. 8. LlTHODESMIUM CONTRACTUM, Bail., HOV. Sp. I 



can give no more accurate idea of this form than is afforded 

 by the figure in the plate, as the specimen was lost before 

 fully examined, and no notes have been found to explain 

 it. It resembles Ehrenberg's Lithodesmium undulatum, but 

 its nature and position have not been fully ascertained. A 

 similar form was found by my father in a salt marsh near 

 Greenport, N. Y. 



Fig. 9. CosciNODiscus ? tenuis, Bail., nov. sp. Shell 

 excessively thin and hyaline, with radiant rows of minute 

 cells, a small central inconspicuous rosette, and a radiate 

 margin ; puncta visible with moderate powers. 



Hab. Para River. 



This species near the margin resembles an Actinocyclus, 

 but shows no colors or rays in the central portion. Sev- 

 eral specimens occur, the puncta being excessively deli- 

 cate and close. The front view is represented in Fig. 9 a. 

 The disc is comparatively large, but so delicate and thin 

 as to be found with difficulty, even when its position is 

 recorded. With the low objectives, it looks like a mere 

 circular haze. 



I cannot omit saying that I feel considerable doubt as 

 to the genus of the form here described. I have seen and 

 carefully studied the specimen from which the figure was 

 taken, and have seen distinctly the characters above given ; 

 but I have also found another and more perfect form, in 

 which there are three distinct marginal processes, which 

 would assign the form to the genus Eupodiscus. This lat- 

 ter specimen is quite as thin and fine, with radiant rows 

 of excessively minute puncta and a margin resembling 



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