1897 - 98 .] Prof. D’Arcy W. Thompson on Marine Faunas. 319 
The two small specimens were immature, and “their characters 
too undefined for satisfactory description” (Trans. Roy. Soc.. 1874 
(pt. 2), p. 749). 
Sir Wyville Thomson (l.c.) speaks of this “singular little urchin 
to which I have given provisionally the name Pourtalesia pliyale.” 
The single specimen collected by the “ Challenger ” measured only 
18 mm. long; it came from 1975 fathoms in lat. 62° 26' S., long. 
95° 44' E. The original description by Wyville Thomson is ex- 
ceedingly brief, and is accompanied by no structural figures. The 
genus is one of the most remarkable of the Spatangoid Echinoidea, 
with peculiarly interesting affinities to certain fossil forms. The 
type species, P. rimanda , was described by Agassiz from 349 
fathoms off the Tortugas, while other species are known, all from 
deep or very deep water, in various parts of the world : one, for 
instance, P. rosea , in the equatorial Pacific ; another, P. laguncula , 
from the North, South, and equatorial Pacific; P. hispida , P. 
ceratopyga , and P. carinata , all from the Southern Ocean in from 
34° to 62° south latitude. In regard to Wyville Thomson’s speci- 
mens no information is given as to their size, but he apparently 
leaves it to be understood that his figure, which measures nearly 
two inches long, is of natural size. This is in sharp contrast to the 
dimensions of the “Challenger” specimen from the Southern 
Ocean, and, together with the inadequacy of the original descrip- 
tion, seems to render the specific identity of the two a very 
doubtful matter. The genus, however, is manifestly ancient, and 
is, in fact, a typical example of a form that is at once ancient, 
abyssal, and widely distributed through northern, equatorial, and 
southern latitudes. 
Phormosoma lioplacardlm , Wyville Thomson. — 
Station 300, lat. 33° 42' S., long. 78° 18' W., 1375 fms. 
„ 164a, „ 34° 13' S., „ 151° 38' E., 410 „ 
„ 235, „ 34° 7'N., „ 138° 0' E., 565 „ 
Pontaster forcipatus, Sladen. — Of this form typical specimens 
are described from localities off the east coast of Nova Scotia and 
the United States, at depths ranging from 1240 to 1700 fathoms. 
These specimens are said (Rej)., p. 46) to be “ remarkably constant 
in general character.” Another Pontaster from 1375 fathoms, lat. 
46° 46' S., long. 45° 41' E., between Marion Island and the 
