TROPICAL PACIFIC HOLOTHURIOIDEA. 153 
The Ecuini were represented by forty species, a very large number in pro- 
portion to the total number of species known. There is no means of determin- 
ing how many specimens were taken as there are no available records on this 
point. Ten of the species brought home are common littoral species of wide 
range but of the other thirty, no fewer than twenty-nine were new when taken 
and all but one of these is from deep water. Undoubtedly the most remarkable 
sea-urchin discovered is Pilematechinus rathbuni, but Centrocidaris doederleini, 
Dialithocidaris gemmifera, Plexechinus cinctus, and Phryssocystis aculeata are 
also of exceptional interest, each being the type of a new genus. 
The HoLoTHuRiaNns were the most generally met with of any of the classes 
of echinoderms and the records show that 953 were in the collections brought 
home. These represented seventy-nine different species many of which are com- 
mon littoral forms of wide range but forty-three were described as new. Of 
course the most remarkable is the extraordinary Pelagothuria natatriz, sole 
representative of a pelagic family and the only echinoderm known to be truly 
pelagic in adult life. Other noteworthy holothurians, knowledge of which we 
owe to these explorations of the ALBaTROss, are two abyssal species of Myrio- 
trochus, the huge Psychropotes raripes, Laetmophasma fecundum, Capheira sulcata, 
and Echinocucumis bitentaculata. 
Summing up for the five classes, we find that the ALBaTrRoss, on her three 
Tropical Pacific expeditions, collected several thousand echinoderms, repre- 
senting 315 species, of which 207, or more than two thirds, were new. The 
increase in our knowledge of the morphology and distribution, both geographi- 
cal and bathymetrical, of the group, which we owe to these expeditions, cannot 
be summarized in this rough and ready way, but one cannot turn the pages 
of the following reports, wherein they are treated, without realizing how great 
it is. 
Iist of the Reports based wholly or in part on the Echinoderms collected by the 
Atpatross Tropical Pacific Expeditions in 1891, 1899-1900, and in 
1904-19065 
CRINOIDS. 
A. Agassiz, 1892. Mem. M. C. Z., 17, no. 2, p. 1-95, pl. 1-32. 
C. Hartlaub, 1895. Bull. M. C. Z., 27, p. 127-152, pl. 1-4. 
A. H. Clark, 1908. Bull. M. C. Z., 51, p. 231-248, pl. 1, 2. 
ASTEROIDS. 
H. Ludwig, 1905. Mem. M. C. Z., 32, 304 pp., pl. 1-36. 
