GEEUS DIFFLUGIA— DIFFLUGIA UECEOLATA. 107 



Absecom, and Lake Hatacawanna, New Jersey; and I also found it abun- 

 dantly in ponds of the Uinta Mountains, Wyoming Territory. 



Ordinarily the shell of Difflugia urceolata strikingly resembles the 

 ancient Roman amphora. The body of the shell varies from a globular 

 shape to a more or less ovoid form. The upper extremity, or fundus, is 

 obtusely rounded or more or less acute, and sometimes it is rounded and 

 more or less acuminate. 



The neck is a short and slight cylindrical constriction from the body. 

 The mouth is large and circular, and frequently truncates the neck ; but, 

 mostly, it is surrounded by a lip of variable breadth, usually more or 

 less reflected, and terminated by a thin delicate edge. Sometimes the neck 

 is more or less everted, and terminates at the mouth without extending in a 

 circular lip or rim. PL XIV, figs. 1-8 ; pi. XVI, figs. 33, 34. 



The size of the spheroidal forms of B. urceolata ranges from about the 

 jijth to the ^„th of an inch in diameter ; the ovoid forms measure from the 

 ith to the ith of an inch in length. 



In the ponds of sphagnous swamps of New Jersey, a variety of JD. 

 urceolata is common, in association with the more ordinary forms, in which 

 the fundus of the shell is provided with usually from three to half a dozen 

 nipple-shaped spines. This constitutes the variety I formerly named D. 

 olla. The shell is commonly of the shape of the spheroidal form of J). 

 urceolata. The spines are mostly blunt, and often terminate in a single 

 stone flake of greater width than the spine at its point of attachment. 

 They are arranged in a circle, more or less regular, around the fundus, 

 usually unaccompanied by a central spine, though occasionally also there 

 is one in this position. They are mostly shorter, less acute, and less eccen- 

 tric than the conical spines in a similar position in D corona. 



Examples of the variety named JD. olla are represented in figs. 10-13, 

 pi. XIV; fig. 32, pi. XVI ; and figs. 28, 29, pi. XIX. 



The shell of Difflugia urceolata is composed, as is generally the case in 

 other species of the genus, of colorless angular particles of quartz-sand, 

 mostly of larger ones scattered with some appearance of regularity, while 

 the intervals are occupied with smaller ones. The surface of the shell, 

 though often uneven, is less so commonly than in some of the smaller 

 species of Difflugia. Frequently larger stones occupy the neck of the shell, 



