1 6 
TH. MORTENSEN, 
(Schwed. Südpolar-Exp. 
really vary to a considerable extent. As correctly described in the »Revis, of Echini» 
they are comparatively slender, slightly tapering, somewhat swelling at the base; 
they are closely set with small thorns, longitudinally arranged, uniting into longi- 
tudinal ridges towards the point (PI. XIV Fig. 18). Between the thorns the ostra- 
cum is covered by rather coarse, bushshaped, somewhat anastomosing »hairs» (Fig. 5) 
— a conspicuous difference from E. nutrix (comp. Taf. XIII Fig. 7, Echinoidea d. 
deutschen Südpolar-Exped.). — The actinal radioles (PL XIV Figs. 7 — 8, x 1) are 
very little specialized, only gradually shorter and with the thorns more or less re- 
duced, sometimes quite smooth; they are not distinctly flattened or curved. 
Fig. 5. Transverse section of radiole of Ausirocidaris canaliculata. 6s /i. 
The secondary spines are generally appressed; those round the radioles are the 
longest, ca. 3 mm., the primary ambulacral spines are a little shorter; the miliary 
spines are scarcely half the length of the primary ones. The spines on the apical 
system are very short, only those surrounding the anal opening are somewhat longer. 
The smaller spines are cylindrical, the larger ones, especially those round the radioles, 
are distinctly flattened and rather broad, not pointed. They are very smooth. 
The pedicellariæ are rather inconspicuous and not very numerous. The large 
globiferous pedicellariæ are typically of the form shown in PL VIII Fig. 32 of the 
»Ingolf»-Echinoidea I; but they may vary not inconsiderably. The side-edges do not 
always proceed as far as the terminal opening, but may end at a shorter or longer 
distance below; but they may also pass almost to the very point of the valve, the 
opening thus lying within the blade, and in this case the opening may be somewhat 
smaller than usual. On the other hand it must be noticed that a form recalling 
that of the large globiferous pedicellariæ of Anstrocidaris Lorioli, figured in the 
»Ingolf»-Ech. I. p. 170 Fig. 7, was never met with in any of the specimens examined 
