48 ON THE ECHINODERMATA OF THE 



the dorsal area of the upper investing membrane, and this forms the common oscular 

 entrance to the cavity, and stands immediately over the anal aperture. Other openings 

 into the infradermal cavity occur upon the abactinal surface between each of the long 

 lateral spines, the apertures being guarded (and can also probably be closed) by a 

 modified spinelet or scale-papilla articulated on the body-frame. There are also a 

 number of small circular punctures distributed over the membrane, which Sars referred 

 to under the style of spiracula, and according to whose observations they are surrounded 

 with a sphincter muscle that would, in all probability, enable them to be opened and 

 closed at will. The superficial dermal covering contains a number of very fine 

 calcareous spicules, and the projecting tips of the supporting paxillary spinelets produce 

 fine asperities over its surface. 



Size. The northern specimens would appear, according to Sars's observations, to 

 be larger than those occurring in the southern portion of the area of distribution. 

 Those taken at Finmark reach the size of 3 inches, whilst specimens from the neigh- 

 bourhood of Bergen seldom exceed 1J-2 inches ; the largest size on record is 4 inches 

 (Lilt ken). 



Colour. Sars remarks that the colour of this species is tolerably variable, the 

 dorsal surface being snow-white, yellowish white, or pale reddish flesh-colour, with a 

 round blood-red eye-spot at the tip of the arm, and the ventral surface of the animal 

 always white. The same author cites a small example from Finmark which was 

 straw-coloured, the tips of the rays orange, a few small scattered spots of the same colour 

 upon the dorsal surface, and the oscular aperture in the centre being also margined 

 with orange. Larger examples from the same coast presented the variations above 

 noted in comparison with specimens from Bergen. 



According to the ' Zoologia Danica,' the animal is more of a brick-red, which 

 colour Liitken also states to have been retained in a large specimen sent to the Copen- 

 hagen Museum by Capt. Holboll. 



Habitat. This Starfish occurs in 40-60 fms. depth at Bergen, and 20-100 fms. 

 off the coast of Finmark ; in 35 fms. off Grand Manan, shelly bottom (Stimpson). 



Premature Stages. We are unfortunately not able to furnish any information 

 upon the characters presented by this species after it has passed the embryonic stage, 

 and prior to the assumption of the adult features. Sars, and also Koren and Danielssen *, 

 have, however, made very valuable observations upon the earlier phases, the two last- 

 named having traced the development of the egg, whilst Sarsf gives very admirable 

 descriptions and figures of the later stages of the larval form. Four of these were 

 found in the infradermal cavity of a specimen inch in diameter from Tromso ; and 

 twelve young, along with two or three eggs, in one 3 inches in diameter from Vadso. 

 In the young individual of l^lf millim. in diameter, the pentagonal form is already 

 apparent, and three pairs of sucker-feet, together with the odd terminal tentacle, are 

 present in each of the radii. In the place of the actinostome there is a large hemi- 

 spherical protuberance or knob-shaped body, equal to nearly one third of the animal's 



* Fauna littoralis NorvegisD, Heft 2. t Oyersigt af Norges Echinodermer, pp. 58-62, pi. vi. 



