PLATE XVIII. 



DIFFLUGIA CONSTRICTA. 



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

 and on a level ; in llu 1 posterior views, they are 1 ilted upward or appear as ordinarily seen, lying on the 

 front U'noaili the inicroscopc. Anterior views appear the same as the latter, as the month is visible 

 through ihc i'.out wall of the shell. The shell mostly composed exclusively of angular quartz sand, 

 ami t he sarcode colorless. 



Flo. 1. Lateral view of an individual with pscudopods protruded. Ditch below Philadelphia, 

 June, 1,-177. COO diameters. 



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

 misplaced by the artist ; the inclined line on the 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 + 



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

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



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

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

 figs. 2, 3. 250 +. 



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

 among moss in the crevices of the pavements of Philadelphia, June, 1S78. 33:! -f-. 



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

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



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



FlG. 14. Lateral view of a specimen, with shell composed of sand and with projected pscudopods. 

 A frequent form found with the preceding. 333 -)-. 



Fir.s. 1"), l(i. Posterior and late ral views of a shell of chitinoid membrane with sand grains. Per- 

 haps pertaining to Cintvopyxia ccornis. Pound with that of figs. 2,3. 250 -f-. 



Pigs. 17, 18. Lateral and posterior views of a shell, composed of sand, stained brown, with a 

 darker cement. Fig. 19. Posterior view of another specimen. Mouth of a cine on Bushkill Creek, 

 Past on, Pa., July, 1878. 333 +. 



PlGS. 20, 21. Lateral and posterior views, with shell of chitinoid membrane incorporated with 

 sand, 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 the fore-lip.) Pgg Harbor, N. J., August, 1878. 333 -f . 



FlGS. 24, 25. Posterior and lateral views. With the preceding. 333 -f-. 



FlGS.23,27. Posterior and lateral views of a specimen with shell of chitinoid membrane, incor- 

 porated at the fundus and around the mouth with sand grains. Sphagnous bog at Absccom, N. 

 J., April, 1876. 250+. 



FlG.28. Lateral view of shell, tilted up to a perpendicular line, composed of chitinoid membrane 

 with large sand grains on the' fundus. With the last. C00+. 



FlGS. 29,30. Posterior and lateral views of a specimen with shell of yellow chitinoid membrane, 

 incorporated with sand. A continuous circle of grains surrounds the mouth, and comparatively large 

 grains occupy the fundus. Absccom pond, April, 1875. 250 -f. 



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

 Sphagnous bug of ISroad Mountain, Pennsylvania, September, 1876. 250 -f-. 



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

 1877. 250 +. 



Puis. 35, 3:1. Lateral and posterior views of a large shell, composed of quartz sand. Vineland, 

 N. J., September, 1S77. 175-)-. 



Puis. 37— 14. Empty shells composed of yellow chitinoid membrane, incorporated with variable 

 proportions of scattered sand grains and dirt. Sphagnum of Absccom cedar swamp, New Jersey. Pigs. 

 :s7, 39, 42, lateral views; tigs. 38, 40, 43, posterior, tilted up, views; figs. 41, 44, posterior views in the 

 normal position. 250 -j-. 



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

 nate at the fundus, and with extended pscudopods. Vineland, N. J., September, 1877. 175 -)-. 



Pi i is. 17, 18. Lateral and posterior views of a large two-spined shell. Absecom pond, New Jersey. 



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



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

 County, Pennsylvania. 175 -f-, 



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

 and with a long, bifid pseudopod. Absecom. September, 1874. 175 -)-. 



Pig. 53. Posterior view of ah individual, with shell having six spines to the fundus, and exhibit- 

 ing a single long pseudopod. Pound .villi the preceding. 175 -p. 



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



Fid. 55. Lateral view of tig. 53. 



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



