74 
Transactions of the Royal Microscopical Society. 
ceased to live long before they were deposited on the sea bottom. 
In some instances it seems probable that the dredge or sounding 
plummet had brought up a portion of some fossil deposit. One of 
the ‘ Challenger ’ soundings, made, I believe, somewhere in the neigh- 
bourhood of Kerguelen’s Land (from a depth of 1950 fathoms),* I 
had an opportunity of examining before it had been acidized, and 
no traces of endochrome could be detected in the few frustules 
observed in it. Many of the valves had the abraded and water- 
worn appearance observable in the fossil Diatomacese. 
In some soundings made during one of the United States 
exploring expeditions (from depths varying from 1189 to 3103 
fathoms), fragments of Coscinodiscus Rex were not uncommon. 
This is undoubtedly a pelagic species, and was first found in the 
Indian Ocean by Dr. Wallich.f In one of the * Challenger’ dredg- 
ings (2900 fathoms) these remains occur in enormous quantities, 
and appear like thin plates of silex ; they are very hyaline, and 
marked with small distant radiant puncta which become scattered 
as they approach the centre. Interspersed with these will be ob- 
served a few small nodules. Mixed with the remains of the discs 
are portions of the connecting zone; on these the punctas are 
smaller, closer, and arranged in transverse parallel lines. I de- 
tected one of these zones nearly ] of an inch in length (and then 
not complete), and of an inch in breadth. The valve to which 
it belonged would not have been less than y- of an inch in diameter. 
In most of these dredgings various species of Asterolampra, Chasto- 
ceros, and Khizosolenia occur, the latter never perfect. It is well 
known that the two last form a large proportion of oceanic surface 
gatherings, and are probably the food of Pteropods, &c., which 
again become the food of various species of whales, and, as their 
siliceous nature prevents their destruction, they are at last voided 
with other fecal matter, and sink to the bottom of the ocean, the 
larger forms being of course much comminuted. — F. K.] 
16th Tribe, Melosirke (Figs. 28, 29). 
The genus Cyclotella (Fig. 28) is composed of species with 
discoid frustules (? valves), and establishes the relationship of the 
Coscinodisceae with the Melosireag. In this last tribe the granular 
endochrome is scattered over the internal surface of the frustule ; it 
is this circumstance that distinguishes it from the preceding tribe. 
* This material contains many of the species figured by Ehrenberg in his 
‘ Microgeologie.’ His samples were collected by Sir James Clarke Eoss during 
his Antarctic expedition in the year 1S47. One- was from “ Pancake Ice,” 
lat. 78° 10' S., long. 162° W., and the other from the sea bottom (1620 feet), 
lat. 62° 40' S., long. 55° W. Ehrenberg’s ‘ Microgeologie,’ tafel 35. 
f I have had the pleasure of seeing a perfect and authentic specimen of this 
fine species ; it measures tV of an inch in diameter. I do not think it has been 
published. 
