GENUS DIFFLUGIA— DIFFLUGIA LOBOSTOMA. 115 



Specimens in which the shell is composed of thin angular siliceous 

 plates, consisting at least in part of diatoms and fragments of others, found 

 usually in sphagnous swamps, are represented in figs. 18-20. 



In several instances I have found specimens of large size, especially 

 in ponds of the Uinta Mountains, as represented in figs. 16, 17, in which 

 the shell was composed of rectangular and oval plates defined by interrupted 

 or dotted lines, the nature of which I did not determine. 



Another variety, observed in a few instances, from Woodstown pond, 

 Gloucester County, New Jersey, had a mammillated shell, as represented 

 in figs. 21, 22. The mulberry appearance of the shell reminds one of the 

 figure of a form designated by Dr. Wallich as Difflugia tuberculatu. The 

 specimen had a six-lobed mouth with a short rim, but the composition of 

 the shell I failed to make out. 



In several instances, once at Morrisville pond, Berks County, and 

 the other in the ditches below Philadelphia, I found peculiar translucent pale 

 yellowish specimens, such as are represented in figs. 25, 26, pi. XVI. The 

 ovoid shell, with trilobate mouth, appeared to be composed of a cancellated 

 membrane, as in the genus Nebela. 



Rarely, also, I have seen a specimen with trilobate mouth, in which 

 the shell appeared to be composed of flocculent dirt, as represented in 

 fig. 29. 



A small specimen, such as I have occasionally seen, with trilobate 

 mouth, and with the shell composed of chitinoid membrane, incorporated 

 with a few scattered quartz particles, is represented in figs. 27, 28. This 

 specimen, from Swarthmore brick pond, accords with the Difflugia tricuspis 

 of Mr. Carter, described as a smaller and less incrusted species than D. pro- 

 teiformis, with trefoil opening of the test, measuring ith of an inch, from 

 Bombay, Ehcenberg regards it as a distinct species, and the name has 

 certainly precedence of the one under which it is here included, but has 

 appeared to me inapj^ropriate-for adoption. 



In perhaps most cases in which I have observed Difflugia lobostoma, 

 especially the ordinary form with trilobate mouth, the endosarc has appeared 

 bright green from the presence of chlorophyl corpuscles ; but in many 

 instances all color except that derived from the food has been absent. 



Difflugia lobostoma commonly ranges in size from the ^ i\x to the r * 5 th of 

 an inch. 



