272 APPENDIX. 



from each of the cross joinings of which proceeds a spine- 

 fasciculus bearing three or four spinelets. The whole dorsal 

 surface of the animal is covered and concealed by a mem- 

 branous tissue supported above the body, like a tent-cloth, 

 by the spinelets, to the tips of which it is attached. A 

 hollow infradermal cavity is thus formed. Neither the anus 

 nor the madreporiform tubercle has any special aperture in this 

 investing membrane ; there is, however, a single large-sized 

 opening, surrounded by a margin of spines, situated nearly 

 over the dorso-central axis. In and out of. this aperture Dr. 

 Stimpson has observed currents of water passing, as in the 

 cloaca of a Holothuria, from which fact he was led to regard 

 the functions of the cavity as subservient to respiration. 1 

 MM. Koren and Danielssen, however, have pointed out that 

 this intermediate space between the double dorsal skin fulfils 

 a further and more important purpose by becoming a chamber 

 in which the development of the eggs and embryos takes 

 place. 2 



Although our knowledge of marsupiation in Echinoderms 

 has recently been largely augmented by^ the additional in- 

 stances which Sir Wy ville Thomson records as occurring in 

 species from southern seas, 3 it is most interesting to find 

 so special an adaptation for the purpose in this truly Arctic 

 asteroid. 



Two specimens only were obtained, being dredged by Mr. 

 Hart in Dobbin Bay. They measure about 60 millims. in 

 their greatest diameter. 



OPHIUROIDEA. 



Ophioglypha Sarsii (Liitken), Lyman. 

 Coll. Feilden: Floeberg Beach, 10 fms. ; Discovery Bay, 

 25 fms. ; Hayes Point. 



An Ophioglypha with mouth-shields shield-shaped, longer 



1 Stimpson, < Marine Invertebrata of Grand Manan,' p. 15, in Smith- 

 sonian Contributions, vol. vi. 



2 Koren and Danielssen, ' Fauna littoralis Norvegise,' Heft 2, p. 58. 



3 Wyville Thomson, ' Journ. Linn. Soc.' vol. xiii* p. 55. 



