324 Notes of Diatomacese in the stomachs of Mollusca. 
Naviculece. 
Navicula Hippocampus, Ehr. 
Ceratoneis Closterium, Ehr. 
CoscinodiscecB. 
Coscinodiscus Patina, Ehr. 
C. lineatus, Ehr. 
Coscinodiscus eccentricus, Ehr. 
Actinocyclus undulatus, Bailey. 
Actinoptyclius senarius, Ehr. 
Actiniscece. 
Dictyocha gracilis, Kg. 
This list will afford some idea of the nature of the deposits 
going on in the Aberdeen bay at the depth and distance from 
land already mentioned. 
The following species were evidently in a living state : — Melo- 
siera sulcata, M. Jurgensii, Synedy'a Icevis, Navicula Hij)pocampus, 
Surirella ?, Coscinodiscus Patina, Actinoptychus senarius, and they 
were also very common ; in this latter respect, however, they were 
not superior to the Dictyocha and Doryphora. 
Of those enumerated, the following are usually met with in 
freshwater: Fragilaria pectinalis, Diatoma flocculosum, Cocconeis 
Pediculus, Cymbella maculata and Gomphonemapohliceforme ; they 
were also much less abundant than the others. Their presence 
is readily accounted for, when it is considered that two large 
rivers, the Dee and Don, besides numerous smaller streams, 
empty themselves into the bay. Mr. Thwaites informs me that 
he has found the Meloseira sulcata both in fresh and brackish 
water. Some of the species mentioned are not uncommon in the 
mud of our harbour. 
Mixed up with the Diatomacece were numerous individuals 
belonging to two or three forms of Foraminifera, also spiculse of 
a species of Grantia and fragments of Ulva, with particles of silex 
in a finely divided state. 
Some of those enumerated have a very extensive distribution : 
Meloseira sulcata has been found at Melville Island, and by 
Dr. Hooker at Victoria Barrier, where Coscinodiscus eccentricus 
and C. lineatus also occur. These and others are abundant in 
guano from Africa and Peru, and are now in myriads mixed with 
the soil of our fields, and their presence may perhaps at a future 
time be a puzzle to some assiduous Philomikros who may be 
ignorant of the history of British agriculture. 
Although temperature may exercise little influence over the 
distribution of Diatomacece, it may not be irrelevant to record 
here that of the sea in the Aberdeen bay, as ascertained by 
Mr. James Stratton, whose observations were made occasionally 
from March 1845 to September 1846 inclusive. The mean tem- 
perature at a mean depth of 24*5 fathoms, four miles from land, 
is 47°' 7 F., being nearly one degree higher than that of the air 
as observed in the vicinity of Aberdeen. The minimum took 
place in March, being 39°*5 F., exactly the mean temperature of 
the ocean according to Sir J. C. Ross. 
