Bd. VI: 4) 
THE ECIIINOIDEA. 
3 
I beg here to tender my best thanks to Professors Hj. Theel, H. LUDWIG, L. 
Doderlein, L. Joubin, G. Pfeffer, Drs. O. Steinhaus, R. Hartmeyer and the 
late Dr. M. MEISSNER, who have with the greatest liberality answered my requests 
for material, loan of type specimens or information on special points. To Mr. H. 
Lynge T am indebted for the identification of some bivalve molluscs, commensalistic 
on some of the Echinoidea in the collection of the South Polar Expedition. 
Fam. Cidaridæ. 
Ctenocidaris n. g. 
The test not very high, the vertical diameter ca. 50 — 60 % of the horizontal 
diameter, not reckoning the generally much elevated anal system. Ambulacra ca. 
Vs as wide as the interambulacra; the pores very close together, the partition-wall 
even generally interrupted. The secondary tubercles very numerous and close, leav- 
ing no naked median space in either ambulacra or interambulacra. In larger speci- 
mens there are 8 — 9 interambulacral, ca. 60 ambulacral plates in each series. The 
apical system ca. 45 % of the horizontal diameter; all oculars excluded from the 
anal system. The peristome ca. 36 — 40 % of h. d.: interambulacral plates on the 
peristome reaching the mouth-edge in larger specimens. The radioles scarcely exceed 
the h. d. in length, rather closely set with small serially arranged thorns; otherwise 
covered with anastoming “hairs”. The actinal radioles very coarsely serrate. Se- 
condary spines cylindrical, clubshaped, those around the radioles more or less flat- 
tened; they are generally rather erect. The pedicellariæ are elongate, with a rather 
small, irregular opening, without end-tooth; only one kind known, probably repre- 
senting the small globiferous form. Spicules of the usual shape. 
Hitherto known only from the Antarctic Ocean. 
The relations of this genus must evidently be sought for among such forms as 
Rhynchocidaris and Notocidaris. The pores and the secondary spines seem to point 
in this direction (the special character of the pores in Rhynchocidaris triplopora is 
not in disagreement herewith). The shape of the actinal radioles is peculiar in each 
of the three genera. The pedicellariæ, unfortunately, cannot be discussed in this con- 
nection, as the only form known from Ctenocidaris is probably the small globiferous; 
but it is the large form of globiferous pedicellariæ which is the more characteristic 
and thus the more important of the two forms. In any case the fact that there is 
no end-tooth on the pedicellariæ of Ctenocidaris is in accordance with the suggestion 
