No. IX. ECHINODEUMATA. 265 



young individuals, and near the tip of the arm, the double 

 series are the most numerous, being generally borne by two 

 or three plates in succession. After these follow two or three 

 (according to age) longitudinal series of separate spines, not 

 quite so long as the ambulacral spines, and tapering slightly 

 at their tips. The middle series, when present, are smaller 

 than the others, and placed midway upon the lateral imbri- 

 cating pieces. At the base of each of the spines of these 

 three series is a circlet of pedicellarise. The ossicles and 

 interspaces of the calcareous network on the abactinal surface 

 of the rays present a very transversely elongate arrangement, 

 in consequence of which the spinelets springing from the im- 

 bricating pieces assume the character (though irregularly) of 

 a transverse position across the arm. The dorsal spinelets, 

 which are much finer and shorter than the ventro-lateral 

 series, are arranged in groups upon the ossicles, and in speci- 

 mens preserved in spirit are more than half-covered by the 

 thick corrugated skin which invests the body. The pedicel- 

 larise are, as a rule, not very numerous upon the dorsal 

 surface. The papulae are single. Upon the disk the spine- 

 lets are more closely placed ; and this, in spirit-examples, 

 gives quite a distinct appearance to that portion of the 

 animal, whilst in some specimens the disk-spinelets .are 

 rather longer than those which are found upon the rays. 



Dr. Liitken is of opinion that this is the species cited by 

 Forbes under the name of Uraster violaceus, from Assistance 

 Bay (Capt. Penny's Expedition). 1 It seems probable to us, 

 also, that the Asterias violacea, in Sabine's Keport on 

 Parry's voyage, is likewise A. gronlandicus, since the Asterias 

 rubens, Fab. (non Linne), also there mentioned, is referable 

 to A. polaris, M. & T. 



Asteracanthion polaris, Miiller and Troschel. 



Some large specimens were taken on the Torske Bank, 

 Greenland, on the outward journey ; and several young 



1 < Vidensk. Meddel. 1857, Overs. Gronl. Echin.' p. 20. 



