Report on the Echinoderms of North-East Greenland. 267 



4, 7 (palœocrystallus), to compare with PI. XV. Figs. 2, 3, 5, 6 (P. 

 typiciis)). — In P. typicus there are two distinct types of cruciform 

 pedicellariæ; those on the lower side of the arms are elongate, with 

 large teeth, especially a series of ca. 5 teeth along the inner median 

 part being prominent, the upper edge being narrow (PI. XV. Figs. 5, 6); 

 those on the dorsal side are considerably smaller, with no prominent 

 median teeth, and with the upper edge broader (PI. XV. Figs. 2—3). 

 In P. palœocrystallus the two forms are less different in size; the 

 larger form (PI. XV. Figs. 4, 7) is less elongate and has only 2—3 

 more prominent median teeth. The smaller form (PI. XV. Fig. 1) 

 is, generally, somewhat more coarsely dentate along the upper edge; 

 this difference is, however, not quite constant. 



I may also add that in both species the three inner adambula- 

 cral spines are single, the inner one being placed at a lower level 

 than the others, more or less hidden within the mouth space 

 (PI. XIV. Figs. 7, 9); from the 4th they are double. 



Evidently the arms of these species, especially typicus, are very 

 fragile; it is seldom to find all the arms of a specimen equal in 

 length, and often it is distinct that the outer part of an arm is 

 regenerated. 



One point still I may call attention to, viz. that the eye spot 

 in P. typicus is exceptionally large; it would evidently be a very 

 favourable object for a detailed study of this structure. In P. palœo- 

 crystallus it is not so large. 



13. Stichaster albulus (Stimpson). 

 PI. XIII. Figs. 1-6. Pl.XIY. Fig.8. PI. XV. Figs. 8-10. PI. XVII. Fig. 12. 



Asteracanthion problema Steenstr. Lütken. 1857. Grønlands Echinod. 



p. 30. 

 Stichaster albulus Duncan & Sladen. 1881. Mem. Echino- 



dermata Arctic Sea. p. 29. PI. II. Figs. 13-17. 



— — Danielssen & Koren. 1884. Norske Nordh.- 



Exped. Asteroidea p. 3. PI. VIII. Figs. 13—15. 



— — Fischer. 1886. Echinodermen. Oesterreich. 



Polarstat. Jan Mayen, p. 32. 



— — Ludwig. 1900. Arktische Seesterne. Fauna 



Arctica. p. 479. 



— — Til. Mortensen. 1903. Echinoderms from 



East Greenland, p. 72. 



— — Michai lovskij. 1903. Echinod. Russ. 



Exped. Spitzbergen, p. 18, 66. 



— — Grieg. 1907. Echinodermata. II. "Fram" 



Exped. p. 10. 



