EHIZOPODA FROM NORTH AND SOUTH AMERICA. 



205 



but until a sufficient number of observiitions have been recorded to clear up 

 this question it would perhaps be advisable to regard A. polypora, Penard, as 

 a variety of A. discoides, Ehrenberg. The following table shows the relation- 

 ship of these species with appro.vimate limits of size : — 





Diameter. 



Aperture. 



1 

 Heiglit. No. of nuclei. 



Arcella discoides, Ehrenberg 



80-150 ,x 



■3 dia. 



1/5 to 1/3 dia. 



2 normally 



>> 



polypora, Penard 



100-200 [X 



•3--4 dia. 



1/4 to 1/3 „ 



8-20 



}> 



megastoma, Penard^ sp. nov. 



190-365^ 



•4-"55 dia. 



1/4 to 1/3 „ 



40-200 



)! 



cwucita sp. nov 



120-135 ti 



•4 dia. 



1/4 dia. 



4 or 5 





Information is required regarding the development of the young of the 

 above species and the number of nuclei present at various stages of their 

 growth. It is possible that the nuclei increase in number by division during 

 the development of an individual. The structure of the tests and the pores 

 around the apertures appear to vary in the A. discoides group within a wide 

 range, the limits of which cannot at present be accurately defined. 



Arcella vulgaris, Ehrenherg. (PI. 15. fig. 5.) 



An unusual form of this species was found which has acute basal angles, as 

 shown in fig. 5. 



Diameter 100-136 //, ; height ^ to ^ the diameter. 

 Distribution. — Princeton, N.J. ; Norfolk, Ya. 



Family Difflugina. 



DiFFLUGiA BICORNIS, Penard, in Mem. Soc. Geneve, xxxi. 1890, no. 2, 

 p. 141, pi. 4. figs. 12-U. (PL 15. figs. 10 & 11.) 



JD. hicuspidata, KliumWer, Zeitschr. f. wiss. Zool. lii. (1891) p. 546, pi. 32. fig. 60. 



D. elegans pars, Penard (8), p. 237, fig., 10. 



? B. acuminata pars, Leidy (6), p. 109, pi. 12. figs. 24-27. 



The majority of the tests observed were furnished with two horns, but 

 three- and rarely four-horned tests also occur ; the two- and three-horned 

 forms are symmetrical, but the fourth horn appears as if interpolated on the 

 latter form (fig. 11). 



Length, without horns, 70-80/* ; breadth of test 60-65//,; horns 20-30 /t 

 in length. 



Distribution. — Grood Ground, Long Island; Palisades and Princeton, N.J. ; 

 Asbury Park, N.J. 



