330 Mr. F. Chapman on the 



either of a single tent-like chamber or of a number of such 

 chambers connected by adherent stoloniferous tubes.'' _ The 

 structure of the test as belonging to the Trochamminince^ is 

 "thin, composed of minute sand-grains incorporated with 

 calcareous or other inorganic cement, or embedded in a 

 chitinous membrane ; exterior smooth, often polished ; in- 

 terior smooth or (rarely) reticulated ; never labyrinthic." 



When a thin vertical section of the test of Wehhina clavata, 

 P. & J., is examined under a low power of the microscope 

 the general form of the test is seen as in fig. 1. The cavity 



Fig. 1. 



Vertical section of the test of Webbina clavata attached to a piece of 

 Gasteropod shell. X 30. 



of the shell is always undivided, whereas in many of the 

 linear-shaped Nubecularice the embryonic or primordial 

 chamber shows a partial or complete septation, somewhat 

 after the manner of the Milioline commencement of an Articu- 

 lina. This character is shown in the figures of Nuhecularia 

 tibia from the clay (Liassic) of Chellaston which illustrate a 

 paper by Professors Jones and Parker *. It will also 

 presently be shown that Vitriwehhina often exhibits a poly- 

 morphine septation in its initial segment, and this can only 

 be seen in the specimens which have the early chambers 

 preserved from injury, and is usually met with in organisms 

 which have afiixed themselves in a recess of the stone to 

 which they are attached f. Vitriwebbina thus shows an 



* Jones, T. E., and Parker, W. K., " On some Fossil Foraminifera 

 from Chellaston, near Derby,'' Quart, Journ. Geol. Soc. vol. xvi. 1860, 

 p. 455, pi. XX. tigs. 49-51. 



t It may here be pointed out that some perfect specimens are met 

 with which do not show any septate commencement ; so that it is ex- 

 tremely probable that we have two types, one of an embryo and the other 

 of a simple bud, according to the alternating series of generation in the 

 Foraminifera. 



