IN THE WAKE OF THE “ CHALLENGER.*’ 
9 
of one form of trilobite.* Some beautiful little urchins were 
also obtained, allied to the Salteria taken by Count Pourtales 
off Florida. “ To an advocate of the 6 continuity of the chalk ’ 
it is pleasant,” says Professor Wyville Thomson, “to see in 
the flesh this little beauty, which has hitherto been reckoned 
among the lost tribes.” 
On Friday evening, Feb. 14, 1873, Santa Cruz was left, 
the weather being fine, and a light breeze blowing from 
N.E. Course westward. On the morning of the 17th, from 
a depth of 2,700 fathoms a mutilated specimen of a new 
Grephyrean was obtained, which was referred by Dr. Suhm to a 
new genus, Leioderma , intermediate between the Sipunculids 
and Priapulids. On the 18th, with 2,220 fathoms of line out, 
there was brought up, attached to a kind of coral, a sponge 
belonging to the Hexactinellidce , but the type of a new genus 
Poliopogon ( 7 roXm'v, white ; irooycov, beard) amadou . Both sur- 
faces were covered with a network of square meshes like that of 
Hyalonema. From its base projected a bush of anchoring 
spicules, each having a barbed end like the anchors on the 
skin-spicules of it. 
Professor Wyville Thomson remarks f that in hot and calm 
weather the t owing-net is usually unsuccessful, for it seems 
that the majority of pelagic forms retire during the heat of the 
day to the depth of a few fathoms, and come up in the cool of 
the evening and in the morning, and, in some cases, in the 
night. The larger phosphorescent animals are often abundant 
during the night around and in the wake of the ship, while 
none are taken in the net in the day. On the afternoon of 
the 26th no less than 3,600 fathoms of rope were payed out, 
the deepest haul by several hundred feet which had hitherto 
been made. For a few previous soundings part of the mud 
had been getting darker, having, too, less calcareous matter on 
analysis, and fewer foraminifera were seen under the microscope. 
Now the latter organisms were entirely wanting, there being 
only a clay mud, like chocolate, remaining for days suspended 
in water. When at last it settled it formed a smooth red- 
brown paste, with no feeling of grittiness to the fingers, “ as 
though it had been levigated with extreme care for a process 
in some refined art.” It was almost pure clay on analysis, 
consisting of a silicate of alumina, sesquioxide of iron, with a 
* See Dr. Suhm’s paper “ On some Atlantic Crustacea from the Challenger 
Expedition.” “ Trans. Linn. Soc.,” New Series. li Zoology,” vol. i. PL XI. 
fig. 4. 
t u Nature/’ vol. viii. p. 29. A family of silicious sponges with six-rayed 
spicules. 
