EEPOET OJf THE HOLOTHUEIOIDEA. 
261 
frondosa, Poslus fabricii, and possibly Psolus phantapus, appear to be distributed round 
or nearly round the pole. 
Only a few Holothurids, viz., Holothuria atra and Holothuria impatiens, are with 
certainty known to be “ circumequatorial,” and Holothuria occidentalis, Holothuria 
rigida, Mulleina parvula, and several others may doubtless be proved to have the same 
wide distribution. Considering the great conformity between the Holothurids in the 
Indian and Pacific Oceans, it does not appear improbable that an exchange of forms is 
stdl going on between the Pacific and Atlantic Oceans, and that this takes place round 
the south coast of Africa. There is great probability that the currents in the Atlantic 
Ocean, as weU as in other seas, transport animals in the larval state from one coast to 
another. No shallow- water Holothurid is, of course, known to be completely cosmo- 
politan. 
Though our present knowledge with regard to the distribution of the Holothurids is 
too insufficient to establish definite features of the different oceans, a few points which 
are probably accurate may be mentioned. 
The Arctic Ocean. — The Synaptidse, in regard to the number of species, are very 
poorly represented. The genus Synapta has only a single representative, Synapta 
inhcerens, and it, besides being very rare, is not a true arctic form. Chirodota Icevis and 
Myriotrochus rinchii, on the contrary, are present in great numbers, and the latter as well 
as Trochoderma elegans, both very strange forms, may be said to give a character to 
the arctic fauna. Among the Molpadidse, Eupyrgus scaher is singular in general 
appearance, and peculiar to the arctic ocean. The Dendrochirotae have about twenty-five 
representatives, but not a single one of a remarkable shape except Echinocucumis typica, 
which is not a true arctic form. However, Cucumaria frondosa, one of the largest 
known Holothurids, abounds in several parts of the Arctic Sea, and gives the fauna a 
singular character, and the same may be said in a higher degree of the genus Psolus, which 
attains its maximum development in the northern seas, the three species Psolus phan- 
tapus, Psolus fabricii, and Psolus squamatus, being the largest known forms of this genus. 
The Aspidochirotse are nearly absent, only two or three forms, Holothuria intestinalis, 
Holothuria tremula [Vj and Holothuria eccdcarea, having been with certainty found in 
the southern part of the arctic region. With a few exceptions, Cucumaria frondosa, 
Holothuria tremula and Trochstoma boreale, the northern Holothurids are almost devoid 
of colouring matters in the integument. 
The Antarctic Fauna is too insufficiently known to admit of any general statements. 
The Atlantic Ocean. — The Atlantic Ocean, which can be divided into several regions, 
the North Atlantic, the South Atlantic, the West Indian and the Mediterranean, contains, 
as may be seen from the tables, a much greater number of shallow-water Holothurids than 
the Arctic Sea, but scarcely one can be said to characterise it. Of course there are many 
species hitherto known only from the Atlantic Ocean, but they do not in general present 
