46 



TH. MORTENSEN, 



(Schwed. Siidpolar-Exp. 



give me his opinion, whether it was really the same species as that described by 

 him as Sterech. margaritaceus, pointing out for him certain minor differences 

 between the two forms. Prof. DöDERLEIN kindly told me that, in spite of these 

 differences, it was certainly identical with the species described by him. Thus, 

 through the direct comparison with the specimen from the »Hassler» as well as with 

 those described by DöDERLEIN, it is made evident that the specimens before me 

 really belong to the species called margaritaceits by these authors. 



DöDERLEIN points out (Op. cit. p. 219) the following main characters as distin- 

 guishing this species from the other species of the genus Sterechiiuis: The height 

 of the test is lower than half the horizontal diameter; all the ocular plates are con- 

 stantly excluded from the anal area; the blade of the globiferous pedicellariae is 

 almost quite open. — The rather considerable material of the species procured by 

 the Swedish Southpolar Expedition, however, necessitates some modifications of 

 these characters of the species. 



As shown by the following measurements of the specimens in hand, the height 

 of the test is, in the larger specimens, generally lower than half the diameter; in 

 one specimen, however, of 54 mm. diameter the height is 30 mm., thus not in- 

 considerably higher than half the diameter. Likewise in the small specimen of 



* Probably a hybrid between St. Agassizii and St. Netwiayeri 



