TH. MORTENSEN, 



(Schwed. Siidpolar-Exp. 



of the relationship of this genus with RItyncIiocidaris and Notocidaris. — To Aii- 

 st7-ocidayis and Eiirocidaris the relation is evidentl}' not so ver\' near; the flattened 

 secondary spines and very little specialized actinal spines of the two latter genera 

 are features which speak against very near relation between Ctcnocidaris and these 

 two genera. 



Ctenocidaris speciosa n. sp. 



PI. I— II. PI. Ill Figs. 1—2, PI. IV Figs. 1—3. PI. XIII. 



Diameter. 



Height. * 



Width of 



Ambu- 

 lacra. 



Interamb. 



Number of Plates. 



Ambu- 

 lacra. 



Interamb. 



Apical 

 system. 



.\nal 

 system. 



Peristome. 



Longest 

 Radioles. 



53** 

 5' 

 5' 

 46** 



43** 

 19** 

 18.5 

 6 



3-5 



26 

 25-5 

 25 

 24 



22 

 9 



9 

 3 



2 



25 



23 123-5) 



23 



\) broken 

 19 



7-5 

 8.5 



3-2 

 2 



H 

 13 

 13 



4.2 

 1.2 

 0.6 



9 

 9 

 9 



The shape of the test is somewhat variable, the height being sometimes only 

 half the horizontal diameter, sometimes — and this seems to be the more general 

 case in the grown specimens — rather more, up to 62 \ of the horizontal diameter, 

 as seen from the above measurements. In younger specimens it is generally equal 

 to half the h. d. The sides of the test are rounded, the upper and lower sides some- 

 what flattened; the border of the peristome is rather strong!)- incurved. 



The ambulacra are distinctly undulating in the upper part. Inside the primar\- 

 tubercle there is, at the lower edge of the plate, another tubercle of about the same 

 size and further one more in the inner corner of the plate, the spaces between these 

 tubercles having quite small, miliary tubercles (carrying pedicellariae); there is thus 

 no naked median space left (PI. XIII Fig. 13). The inner of the secondary tubercles 

 is developed only at the ambitus, not in the actinal or abactinal part; in younger 

 specimens only the outer secondar}- tubercle is developed, the interporiferous zone 

 of the ambulacra thus being covered by 4 series of tubercles, as is also the case 



* In the height is not included the elevated anal system. 

 ** The specimens thus marked were not denuded; some of the measurements are therefore not fully 

 reliable (e. g. the peristome) or even omitted and the number of the ambul.acral plates not quite e.xact. 



