PLATE XVII. 



DIFFLUGIA CORONA. 



All the figures were from living specimens ; the shell composed of angular quartz sand and the 

 earcode colorless. 200 diameters, except when specially indicated. 



Fig. 1. Individual with extended psendopods ; the shell with seven spines to the fundus, of which 

 five are visible iu the lateral view. The mouth was furnished with twelve points or teeth and as many 

 intervening sinuses. The somewhat palmate pseudopods were spread outwardly on the inclined border 

 of a glass cell. A common form in Swarthmore brick-pond, Delaware County, and in ditches below 

 Philadelphia. 



Figs. 2-4. Common forms, from Lake Hattacawanna, Morris County, New Jersey, October, 1874. 



Fig. 2, lateral view of an individual with extended pseudopods; shell with seven spines to the 

 fundus aud fifteen teeth to the mouth. 



Fig. 3. Inferior view of another individual, exhibiting the mouth and extended pseudopods. 

 Shell with seven spines to the fundus and fourteen teeth to the mouth. A similar specimen, 0.248 mm. 

 high and 0.24 mm. broad, had seven spines to the fundus and twelve teeth to the mouth. 



Fig. 4. Upper view of a specimen with eleven spines to the fundus. Mouth 0.10 mm. in diameter 

 with sixteen brown teeth. 



As represented in the figures, while the body of the shell is colorless, the spines and border of the 

 mouth are frequently stained of a ferruginous brown. 



Figs. 5, 6. Two views of the same individual ; fig. 5, lateral view, with extended pseudopods, and 

 four spines to the fuudus ; fig. 6, inferior view exhibiting the mouth with fifteen teeth. Ditch below 

 Philadelphia, September, 1875. 



Fig. 7. Lateral view of a specimen with an oblique mouth as in Difflugia constricta, but furnished 

 with twelve teeth, and having a single spine to the fuudus. The only specimen of the kind seen. 

 Swarthmore brick-pond, March, 1875. 



Fig. 8. Inferior view of a specimen exhibiting the mouth with six teeth. The fundus of the 

 shell had seven comparatively short spines. Jacksonville, Fla., March, 1875. 



Fig. 9. Lateral view of a slightly unsymmetrical specimen with a single spine to the fundus. 

 The mouth had twelve teeth. Ditch below Philadelphia, September, 1875. 



Fig. 10. Lateral view of an individual with a pair of widely divergent spines to the fundus, and 

 with extended pseudopods. Mouth with twelve teeth. With the preceding. 



Fig. 11. An unusually unsymmetrical specimen. Lateral view with extended psendopods. Seven 

 spines to the fundus and sixteen teeth to the mouth. Atco, N. J., September, 1877. 



Fig. 12. Six-lobed mouth of a specimen which had seven spines to the fundus. The shell was 

 0.33 mm. in diameter. Lake Hattacawanna, New Jersey. 



Fig. 13. One of the spines from the same specimen, showing a lance-head-like flake at the end. 

 375 diameters. 



Fig. 14. Three teeth from a specimen like that of tig. 0, showing terminal colored sand grains. 



