166 THE AUSTRALIAN NATURALIST. 
NOTES AND COMMENTS. 
ExcHANGES.—WaATER Beetites.—Mr. F. B. Brown, 
Claremont, Holywood, England, wants Australian watér 
beetles, and would be glad to obtain specimens from any 
of our members. He will give in exchange British beetles. 
Mr. Froggatt will take charge of and transmit specimens, 
Ants, Bees, Wasps.—Specimens of any of these, their 
nests and anything illustrative of their economy, are wanted 
by Mrs. Maria Sadownikowa, Volhonka Antipievsky ro, 
Moscow, Russia. This lady is connected with the Moscow 
University for Women, and offers suitable exchanges, Full 
particulars may be ascertained from Mr. Froggatt. 
Nore ON THE FUNCTION OF THE VENTRAL FINS IN 
Nomeus gronovii.—This fish, which is known as the “Por- 
tuguese- Man-o’ -War Fish,” is well known as a small pelagic 
species, possessing a great geographical distribution. It 
occurs on the coast of New South Wales, most noticeably: 
while the Siphonophore known as “Portuguese-Man-o'- 
War,” or Physalia, is plentiful, swimming in the company 
of this animal. The fish is chiefly remarkable on account 
of its large ventral fins, which fold in a deep abdominal 
groove, as in the larger scombroid, Gasterochisma melam- 
pus, Richardson. In regard to these fins, Goode and Bean 
write*: “The large fan-shaped ventrals are used as support 
in resting on the bottom; and in swimming they are gener- 
ally closed in their groove, unless the fish is moving leisure- 
ly, when they may be partly expanded.” From this, one 
would, perhaps, gather that the first-mentioned use is 
the main function that these fins subserve, and Jordan and 
Evermann, in their great work on the “Fishes of North 
and Middle America,” evidently intend this idea to be 
conveyed when they state,t on the authority of the pre-~ 
viously-mentioned authors: “The large fan-shaped yven- 
trals are used in support in resting on the bottom. In swim- 
ming, they are usually closed in their groove,” particularly, 
as no mention is made of the latter portion of the state- 
ment of Goode and Bean. My purpose in writing this note 
is to state that it appears to me that the sole purpose of 
the development of these fins to such a large size, is to 
enable the fish to preserve its cenesae while slowly 
* Oceanic Ichthyology (1895), p. 220. 
we Bull. GS: Nat. Mus., No. 47, Bese a) :p. 940, (Footnote) 
Mas? hw J 
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