NO. 4 



FORAMIXIFERA CUSHMAN 



15 



used in description, the apcrtiiral view (fig. 2>b) in the plane of coihng, 

 with the apertural face toward the observer, and the side view at right 

 angles to the plane of coiling, the two sides being alike. The 

 periphery is the outer edge of the test. The last-formed chamber in 

 most foraminifera has the aperture, and there is usually developed a 

 distinct apertural face. The periphery of the test may have a definite 

 peripheral-angle or be carlnate or keeled. The wall of the test may be 

 perforate or imperforate, and variously ornamented on the exterior. 

 The number of chambers in the last-formed coil is often distinctive. 



Pio. 3. — A bilaterally symmetrical form of test, showing a, side view ; 

 b, apertural view. 



Pig. 4. — A trochoid form showing a. dorsal view; b, ventral view, 

 and c, side or peripheral view. 



In the Rotaliidae, particularly, the trochoid form of test is common, 

 sometimes called " rotaliform." In this (fig. 4) it is possible to dis- 

 tinguish a dorsal side and a ventral side (the latter carrying the 

 aperture). The edge view may be spoken of as the side viczv or 

 peripheral viezc. There is a considerable modification, the dorsal side 

 sometimes being the concave one. 



In the Lagenidae there may be a side z'iczv and apertural viez^' in 

 such forms as Lagena (fig. 5) and Nodosaria (fig. 6), and in coiled 

 bilateral forms such as Cristcllaria ( fig. 7), with irregular genera such 

 as Uvigerina (fig. 9), and Polymorphina (fig. 8), the side views are 

 not all ahke. 



