PLATE XVIII. 



DIFFLUGIA CONSTEICTA. 



In the lateral views of the specimens, they occupy the natural position with the mouth downward 

 and on a level ; in the posterior views, they are tilted upward or appear as ordinarily seen, lyiug on the 

 front beneath tho microscope. Anterior views appear the same as the latter, as the mouth is visible 

 through tho front wall of the shell. Tho shell mostly composed exclusively of angular quartz sand, 

 and the sarcode colorless. 



Fig. 1. Lateral view of an individual with pseudopods protruded. Ditch below Philadelphia, 

 June, 1877. 500 diameters. 



Figs. 2, 3. Two views of the same specimen ; the former posterior, tho latter lateral (inadvertently 

 misplaced by the artist; the inclined line on tho right should have been horizontal). From moss in the 

 fork of an apple tree, Swarthmore, November, 1877. 250 diameters. 



Figs. 4,5. Lateral and posterior views of the same specimen. Sphagnous swamp, Vineland, N. 

 J., September, 1876. 250 +. 



Figs. C, 7. Lateral and posterior views of the same (the former misplaced by the artist ; tho 

 inclined line on the left should be horizontal). Fort Bridger, Wyoming Territory, July, 1877. 250 -)-. 



Figs. 8, 9. Posterior and lateral views of a shell composed of yellowish chitiuoid membrane, incor- 

 porated with scattered sand, and a continuous circle of grains around the mouth. Found with that of 

 figs. 2, 3. 250 +. 



Fig. 10. Posterior view of a shell composed of chitiuoid membrane with sand and dirt. From 

 among moss in the crevices of the pavements of Philadelphia, June, 1378. 333 +. 



Figs. 11, 12. Posterior and lateral views of an individual with extended pseudopods. Shell as in 

 the preceding. From among moss of (ho pavement in the yard of my house, June, 1878. 333 -{-. 



Fig. 13. Posterior view of the same specimen in (he natural position, or not tilted forward. 



Fig. 14. Lateral view of a specimen, with shell composed of sand and with projected pseudopods. 

 A frequent form found with the preceding. 333 +. 



Figs. 15, Hi. Posterior anil lateral views of a shell of chitiuoid membrane with sand grains. Per- 

 haps pertaining to Ccntropyxis ccornis. Found with that of iigs. 2, 3. 250 -f-. 



FlGS. 17,18. Lateral and posterior views of a shell, composed of saud, stained brown, with a 

 darker cement. Fig. 19. Posterior view of another speciuien. Mouth of a cavo on Bushkill Creek, 

 Fasten, Pa., July, 1878. 333 -f-. 



Figs. 20,21. Lateral and posterior views, with shell of chitiuoid membrane incorporated with 

 saud, diatoms, etc. China Lake, Uinta Mountains, August, 1877. 250 -)-. 



Figs. 22, 23. Posterior and lateral views. (Correct outlines; with no constriction nor abrupt 

 projection of tho fore-lip.) Egg Harbor, N. J., August, 1878. 333 +. 



Figs. 24,25. Posterior and lateral views. With tho preceding. 333 -f. 



Figs. 26, 27. Posterior and lateral views of a specimen with shell of chitiuoid membrane, incor- 

 porated at tho fundus and around (ho mouth with sand grains. Sphagnous bog at Absccom, N. 

 J., April, 1876. 250 -f. 



Fig. 28. Lateral view of shell, tilted up to a perpendicular line, composed of chitiuoid membrane 

 with large sand grains on tho fundus. With tho last. 500 -f . 



Figs. 29, 30. Posterior and lateral views of a specimen with shell of yellow chitiuoid membrane, 

 incorporated with saud. A continuous circle of grains surrounds the month, and comparatively largo 

 grains occupy the fundus. Absecom pond, April, 1375. 250 -(-. 



Figs. 31, 32. Posterior and lateral views of a shell of chitiuoid membrane with incorporated sand. 

 Sphagnous bog of Broad Mountain, Pennsylvania, September, 1876. 250 -f-. 



Figs. 33,34. Lateral and posterior views of a similar specimen. Vineland, N. J., September, 

 1877. 250 +. 



FlGS. 35, 36. Lateral and posterior views of a large shell, composed of quartz sand. Vineland, 

 N. J., September, 1877. 175 -f . 



Figs. 37-44. Empty shells composed of yellow chitiuoid membrane, incorporated with variable 

 proportions of scattered sand grains and dirt. Sphagnum of Absecom cedar swamp, New Jersey. Figs. 

 37, 39, 42, lateral views; tigs. 3r<, 40, 43, posterior, tilted up, views; tigs. 41, 44, posterior views in the 

 normal position. 250 -f-. 



Figs. 45,46. Lateral and posterior views of a large individual with shell of quartz sand, acumi- 

 uate at tho fundus, and with extended pseudopods. Vineland, N. J., September, 1377. 175 -f-. 



Figs. 47,48. Lateral and posterior views of a large two-spinod shell. Absecom pond, New Jersey. 



Fig. 49. Posterior view of a three-spiued specimen. With the last. 175 -f. 



FlGS. 50, 51. Posterior and lateral views of a two-spined individual. Wind Gap, Northampton 

 County, Pennsylvania. 175 -)-. 



Fig. 52. Posterior view of an individual, with shell having a row of live spines to the fundus, 

 and with a long, bifid pseudopod. Absecom, September, 1374. 175 -f-. 



Fig. 53. Posterior viow of an individual, with shell having six spines to the fundus, and exhibit- 

 ing a single long pseudopod. Found with, the preceding. 175 -f-. 



Fig. 54. Posterior view of another specimen, with four spines. With the preceding. 175 -)-. 



Fig. 55. Lateral view of lig. 53. 



Figs. 56, 57. Two spines, showing the lance-head -like flake at their termination. 500 -J-. 



