Species of 'British Echinodermota. 105 



on the aboral surface of the disk, over the origin of each arm. 

 No interradial plates (in the British genera) in the inferior in- 

 terbrachial spaces. 



Genus II. Astrophyton, Linck. 



Disk thick, pentagonal or round. Arms five, dichotomous 

 from near the base, the branches again and again subdividing, 

 until each arm terminates in innumerable very slender, filamen- 

 tous branchlets. Under surface of arms with a transverse row of 

 short spines to each joint, some of the spines provided with hook- 

 formed processes. No interradial plates. Ovarian apertures 

 ten, two in each interbrachial space. Oral plates bordered with 

 spine-like papillae, which increase in length towards the mouth. 



Astrophyton Linckiiy Miiller & Troschel. 



1733. Astrophyton scutatum, Linck, de Stellis marinis, part., pi. 19. no. 48. 



1766. Asterias caput-Medusce, Linn. Syst. Nat. 1101,^arif. 



1777- Astrophyton arborescens, Pennant, Brit. Zool. vol. iv. p. 67. no. 73 



{but not of Rondeletius nor of Miiller and Troschel). 

 1842. Astrophyton Linckii, Miiller & Troschel, Syst. der Asteriden, p. 122» 



Astrophyton Linckii is confined to the seas of Scandinavia and 

 Shetland. We believe that it has not been procured in the 

 latter locality since the publication of Forbes^s work. In our 

 dredgings to the east and north of the Shetland group, we have 

 not seen a trace of the species ; and the fishermen, to whom we 

 showed Forbes's figure, were unacquainted with it. It would 

 seem, therefore, that the species is only to be found on the 

 western side of the islands. Dr. Charlton has kindly given us the 

 following information respecting the Astrophyton which he pro- 

 cured : — " As far as I can recollect, my specimen of the Astro- 

 phyton was obtained on the north-western coast of Shetland; 

 but, as it is twenty-nine years ago, I am not certain ; for I did 

 not get it myself, but it was procured by William Cameron, Esq., 

 of Belmont, in Unst, who died about twenty-five years ago. 

 The specimen was very large and fine, and in very perfect con- 

 dition. In those days the fishermen knew it well ; and I almost 

 think, if my memory deceives me not, that I saw in 1852, twenty 

 years after my first visit, a small specimen at the ' buidie ' at 

 Stennis, in Northmavine.^' 



Genus III. Asteronyx, Miiller & Troschel. 



Disk pentagonal, naked, without scales or granules; two 

 radiating ribs over the origin of each arm. Arms long and 

 slender, undivided, without scales, convex above, flat beneath. 

 Spines in transverse rows, the larger furnished with hooked pro- 

 cesses. No interradial plates. Oral plates bordered with papil- 



