52 G. 0. SARS, (sam 
It is thus a very considerable bulk of Caspian Crustacea, that will lie 
before me, and I hope that a careful investigation of this vast material will 
prove to be of considerable interest, both in systematic and biological 
respects, and that several fundamental conclusions relating to the early 
history of the Caspian Sea may be hence derived. I think, however, it may 
be convenient to delay such a general discussion until the completion of 
the systematic investigation of the several groups. On this occasion I only 
wish quite briefly to indicate the general suggestions to which a preliminary 
examination of the specimens has led me, and which I hope subsequently 
to be enabled to support by more reliable facts. 
The fauna of the Caspian Sea is, I believe, derived from 3 very differ- 
ent sources. One part is of true arctic origin, and constitutes the remnant 
of the primitive fauna prevailing at the early time, when a connexion between 
the Caspian Sea and the Polar Sea may have existed. Another part of the 
fauna is of a more southern character, and may have immigrated, at a much 
later period from the Black Sea and the Mediterranean; a direct connexion 
being supposed to have existed at that time. A third part of the fauna, 
finally, constitutes a number of true fresh-water forms, which have adapted 
themselves to living in somewhat brakish water, at the estuaries of the 
great rivers debouching in the Caspian Sea. The abyssal region of the Cas- 
pian Sea remains still, I believe, nearly quite unexplored. I am, however, 
‘much inclined to believe that, on a closer investigation, the great depths of 
that basin will be found to contain a peculiar abyssal fauna exhibiting a 
purely arctic character. 
On entering upon an investigation of the carcinological fauna of the 
Caspian Sea, I have thought it right to treat of each group separately. The 
present part comprises only a single family of the Schizopoda, viz., the My- 
side. It will be shortly succeeded by 2 other parts, the one treating of the 
Cumacea, the other of the Amphipoda, and perhaps subsequently a 4th part 
will be added, treating of the lower Crustacea, the Entomostraca. 
MYSIDZ. 
As is well known, the Myside form a family of the lower stalk-eyed 
Crustacea, and belong to the subdivision generally termed Schizopoda, on 
account of the legs being biramous, or provided with greatly developed exo- 
podites acting as powerful swimming organs. Of higher stalk-eyed Crusta- 
cea only 2 species of the genus Astacus have hitherto, according to a kind 
communication by Mr. Herzenstein, been recorded from the Caspian Sea, 
viz., Astacus leptodactylus and A. pachypus, both being evidently fresh- 
he T. XIII, p. 400. 
