SECT. ii. THE MILIOLA. 3 1 



which is made up of a series of half turns arranged 

 symmetrically on its two sides. Each half turn is 

 longer and of greater area than that on the opposite 

 side, so that each turn of the spire has a tendency to 

 extend itself in some degree over the preceding one, 

 which gives a concave instead of a convex border to 

 the inner wall of the chamber. The sarcode body of 

 the Miliola consists of long segments which fill the 

 chambers, connected by threads of sarcode passing 

 through the tubular constrictions of the shell. As the 

 animal grows, its pseudopodia extend alternately now 

 from one end, and now from the other extremity of the 

 spiral, and by them it fixes itself to seaweeds, zoophytes, 

 and other bodies, for these Foraminifera never float or 

 swim freely in the water. The genus Miliola is more ex- 

 tensively diffused than almost any other group of Fora- 

 minifera ; they are most abundant between the shore and 

 a depth of 150 fathoms, and are occasionally brought 

 up from great depths. Beds of miliolite limestone show 

 to what an extent the Miliola abounded in the seas of 

 the Eocene period ; but the type is traced back to the 

 Lias. 



The genus Peneroplis is distinguished by a highly 

 polished opaque white shell ; its typical form is an ex- 

 tremely flat spire of two turns and a half opening 

 rapidly and widely in the last half whorl. It is strongly 

 marked by depressed bands which indicate the septa or 

 shelly partitions between the chambers in the interior. 

 The polished surface of the shell is striated between 

 and transversely to the bands by parallel platted-look- 

 ing folds T ^-o of an inch apart. But the peculiarity of 

 this shell and its congeners is, that the partitions be- 

 tween the chambers in its interior are perforated by 

 numerous isolated and generally circular pores which 

 in this compressed type are in a single linear row. 

 Their number depends upon the length of the partition 



