208 THE ATLANTIC. (CHAP. II. 
chambers are closely and minutely perforated. The external 
surface of the wall is nearly smooth, and in particularly well- 
preserved tow-net specimens spines may be detected closely re- 
sembling those of Globigerina and Orbulina, but more thinly 
seattered and apparently somewhat more delicate. Pulvinu- 
lina Menardii, an example of which is here figured in the con- 
dition in which it is usually met with in the ooze (Fig. 48), 
has a large discoidal depressed shell, consisting of a series of 
flat chambers overlapping one another, like a number of coins 
laid down somewhat irregularly, but generally in a spiral; each 
chamber is bordered by a distinct somewhat thickened solid 
Fig. 48.—Pulvinulina Menardii, D’Orsteny, a the upper, 0 the nuder surface. Thirty times 
the natural size. Dead shells from the bottom, at a depth of 1900 fathoms. 
rim of definite width. On the lower surface of the shell the 
intervals between the chambers are indicated by deep grooves. 
The large irregular opening of the final chamber is protected 
by a crescentic lip, which in some specimens bears a fringe 
of spine-like papille. This form is almost confined to the 
warmer seas. It is very abundant on the surface, and still more 
so during the day at a depth of ten to twenty fathoms in the 
Mid-Atlantic; and it enters into the composition of the very 
characteristic “ globigerina ooze” of the “ Dolphin Rise” in al- 
most as large proportion as Globigerina. Pulvinulina Miche- 
liniana is a smaller variety: the upper surface of the shell is 
flattened as in P. Menardiz, but the chambers are conical and 
