472 THE VOYAGE OF H.M.S. CHALLENGER. 



"Triton" Expedition: 



Station 2. In the Faeriie Channel. August 5, 1882, Lat. 59° 37' 30" N., long. 6° 

 49' 0" W. Depth 530 fathoms. Bottom temperature 46 c -2 Fahr. 



la. Pteraster militaris, var. prolata, Sladen. 



Pteraster militaris, var. prolata, Sladen, Trans. Roy. Soc. Edin., vol. xxxii. p. 153, pL xxvi. fig. 1. 

 This variety is characterised by the following points : — The great length and narrow- 

 ness of the rays. R > 3 r ; E = 58 to 60 mm. ; r = 18 mm. ; breadth of a ray at the 

 base, 18 to 22 mm. extreme measure. The abactinal paxillae appear usually to have one 

 of their spinelets much more robust than the two or three companion spinelets, which are 

 remarkably fine and delicate, and the tips of the spinelets can scarcely be said to protrude 

 through the supradorsal membrane, notwithstanding that this latter is placed loosely 

 upon them and much wrinkled. Two or three lineal series of paxillae are more or less 

 clearly distinguishable along the sides of the rays. On the actinal surface the segmental 

 apertures are remarkably large, and the aperture-papillae are much broader and more 

 robust at their proximal portion than in Pteraster militaris. In the armature of the 

 adambulacral plates the inner three spines of each transverse comb form a line oblique to 

 the furrow, the comb being curved aborally at the margin of the furrow, and the position 

 of these spines upon the adambulacral plate being also oblique in relation to the plane of 

 the ray. The actino-lateral spines are very short, and the outer portion of the web which 

 proceeds from the outermost spine of the adambulacral armature, i.e., the membranous 

 continuation of the transverse comb upon the actinal membrane, is much more prominent 

 than in the typical form of the species, and extends up to the margin of the lateral fringe. 

 Although these differences may appear insignificant verbally, they produce when combined 

 a striking facies, the characters of which can hardly be explained, as being simply the 

 modifications of the normal form consequent on the conditions of a deep-water habitat, 

 since an example of Pteraster militaris from 530 fathoms from a neighbouring station, 

 differs in no way from the normal form. 

 Locality. — " Triton" Expedition : 



Station 9. In the Faeroe Channel. August 23, 1882. Lat. 60° 5' 0" N., long. 6* 

 21' 0" W. Depth 608 fathoms. Bottom temperature 30°-0 Fahr. 



Remarks. — This is a remarkable form, differing greatly in general appearance from the 

 normal type of Pteraster militaris ; and although it accords in the main with the diag- 

 nostic formula of that species, the majority of the characters differ more or less in degree. 

 It is not improbable that a series of examples might ultimately warrant its being ranked 

 as a distinct species ; but for the present I prefer to place the solitary specimen known 

 to me as a variety of Pteraster militaris, until further material is available, a course 

 which is sufficient to identify the form and at the same time indicate the nearest specific 

 affinities. 



