48 TH. MORTENSEN, (Schwed. Stidpolar-Exp. 



surrounded by numerous smaller plates. The character that the ocular plates are 

 all excluded from the anal area is, unfortunately, not constant. Certainly it is 

 generally the case, which then gives a good distinguishing character, but in some of 

 the specimens in hand, which I am otherwise unable to distinguish from the typical 

 form, one or even two ocular plates are in contact with the anal area, viz. in two 

 specimens Ocular I, in one specimen (Stat. 20) Oculars I and V. The latter speci- 

 men, however, is probably a hybrid between 5/. Agassizii and Neumayeri. (The 

 shape of its test is as in Agassizii, but the secondary tubercles on the actinal side 

 are less prominent than is generally the case in Agassizii, and the central plate is 

 quite indistinct as is the case in the larger specimens of Neumayeri. There are 

 numerous spicules as in Agassizii; the globiferous pedicellaria; are of the form 

 typical in Agassizii. — It may be noticed that St. Neumayeri is represented from 

 the same station.) Of the two other specimens one is that mentioned above, in 

 which the scrobicular areas are separated throughout the whole series (Stat. 16), the 

 other is a small specimen. 29 mm. (Stat. 22). As there is evidently no reason for 

 regarding these specimens as hybrids, it must be conceded that the character of all 

 the ocular plates being excluded from the anal area is not quite constant; in most 

 cases it is found, however. — Generally there are distinct genital papillae, as in the 

 other Sterec/iinus-species. The genital openings are present already in the youngest 

 specimen, 11 mm. diameter. (A still younger specimen, 7 mm., has likewise the 

 genital openings developed; the identification of this specimen is, however, not 

 certain.) 



The peristome is rather small, generally smaller than in diadcma. The buccal 

 plates usually carry one or two small spines. 



The spines are like those of diadema; they are very fragile as in all the Ster- 

 sc/iimis-species. The secondary spines are upon the whole slightly longer than those 

 of diadema; they are slender and finely thorny as in that species, ending in a small 

 central thorn or gradually tapering to a point; the latter case seems always to occur, 

 where the point has been restored, which is very often the case (PI. XVI. Figs. 

 7, 13). (The mark, from where the restored part begins, is very distinctly seen by 

 microscopical examination.) 



The globiferous pedicellariae have generally the blade almost quite open, as 

 stated by D5DERLEIN; but sometimes there are crossbeams over the lower half of 

 the blade, or even almost to the end of it — and both kinds may be found in the 

 same specimen. The poison-glands are single, but with double efferent duct (PI. XVI 

 Fig. 15), as is also the case in the other Sterec/iinus-species, in marked contrast to 

 Notechinus, where the glands are double. DODERLEIN describes the tridentate pedi- 

 cellariae as having almost parallel side-edges; this is, however, generally the case 

 only in small specimens, whereas in larger ones the shape of the valves is that 



