24 TH. MORTENSEN, (Schwed. Südpolar-Exp. 



in canaliailata the 2 — 3 lower ones are confluent. Also the number of ambulacral 

 plates corresponding to an interambulacral plate at the ambitus is a little larger, 

 7 — 8 against 6 — 7 in canaliailata of a corresponding size. 



The apical system is, upon the whole, as in canaliciilata, only the genital and 

 ocular plates with the outer side somewhat less prominent; the large female genital 

 openings also less intruding in the median interambulacral line (Fig. 6). In the spe- 

 cimen of II mm. diameter the ocular plates are still all excluded from the periproct; 

 in canaliailata 2 — 3 ocular plates are in contact with the anal plates already at a 

 size of 10 mm. diameter. The genital openings have not yet appeared in the spe- 

 cimen of 14 mm., whereas in canaliciilata they have appeared at that size and are 

 about to appear already in a specimen of 11 mm. diameter. — The anal area is flat 

 in the young specimens, whereas in young canaliciilata, it is distinctly elevated. In 

 the larger specimen it is, however, also somewhat elevated. 



The peristome has the same character as in cajialici/lata, the interambulacral 

 plates reaching the mouth-edge. There are 14—15 ambulacral plates on the peri- 

 stome in the larger specimen; the smallest specimen has 7 — 8 ambulacral plates in 

 each series, and the interambulacral plates do not fully reach the mouth-edge as yet. 



The radioles are about twice the length of the horizontal diameter of test, thus 

 considerably longer than usually in canaliciilata. They further differ from those of 

 canaliciilata in being provided, in the lower part, with some conspicuous, irregularly 

 arranged thorns (PI. Ill Figs. 3—5); the outer part is set with numerous small thorns, 

 arranged in longitudinal series, as in canaliciilata. The structure of the radioles, as 

 shown in sections, is the same as in canaliciilata. The actinal radioles (PL XIV 

 Figs. 4, 12 — 13) are not specialized; they are generally thorny, but may be quite 

 smooth. The larger thorns occur only on the abactinal radioles. The secondary 

 spines do not differ from those of canaliciilata either in shape or in length. 



The pedicellariae differ only very slightly from those of canaliciilata. In the 

 large globiferous pedicellariae the side-edges do not generally reach the opening 

 (PL XIV Fig. 15), but this is not quite constant, and in canaliciilata forms nearly 

 approaching it may occur. The small globiferous pedicellariae (PL XIV Figs. 5, 14) 

 occur in a short and an elongate form, with transitional forms — much as in canalicii- 

 lata. — The spicules of the tube-feet do not afford any feature of specific value. 



The color as in canaliculata. 



The three specimens were dredged at St. 58, South of West Falkland, at 52° 

 29' Lat. S., 60° 36' Long. W. in a depth of 197 m. (bottom sand and gravel; 

 bottom temperature -(- 4'.i). 



It may appear somewhat hardy thus to establish a new species of the genus 

 Aiistrocidaris, seeing that the species canaliculata is maintained to be so very va- 

 riable as also to include Lorioli as a synonym. That this alleged great variability 



