46 Proceedings of the Royal Physical Society. 



though often ignored by the cabinet zoologist, are of great significance to the 

 field biologist, and show the futility of basing specific characteristics on colour. 

 Very good examples of this are seen in species of Pentaceros and Gulcita 



We would like here to draw attention to a peculiar association or 

 commensalism which, although it has been observed in Holothurians, has 

 so far escaped notice in Asteroids, viz., that between a species of Fierasfer 

 (as yet unidentified) and Pentaceros linclci. 



While dissecting specimens of this species of starfish for drying, we were 

 surprised to find occasionally a small Fierasfer alive; careful dissection 

 showed that these fish, occasionally in pairs, inhabited the stomach of the 

 starfish, but were quite healthy and normal; in fact, we were able to 

 keep them alive for some time in tanks. On placing some of these large 

 starfish in the same tanks, it was possible to watch the Fierasfers passing out 

 and in at the " mouth " of the Pentaceros. This disappearance and reappear- 

 ance continued daily, so that we feel quite in a position to say that it is 

 another example of commensalism, similar to that between fish and Holo- 

 thurians, added to our knowledge of " associations." 



Several very interesting specimens of Linckia diplax showing different 

 stages in the regeneration of lost arms occur in the collection. Especially 

 noteworthy are the comet-forms. 



We are glad to have this opportunity of expressing our indebtedness 

 to Professor J. Arthur Thomson, for kindly granting us laboratory accom- 

 modation in his department in the University of Aberdeen, as well as 

 for other facilities ; and we wish also to thank Professor F. Jeffrey Bell, 

 for allowing us to compare our specimens with those in the British Museum, 

 and for the interest he has taken in the collection. 



For general utility we have adopted the classification given by Sladen in 

 his report on the "Challenger" asteroids {"Challenger" Reports, Zoology, vol.xxx.), 

 although a better classification has since been published in Bronn's Thierreich. 



In accordance with the former, the following table shows the general 

 relationships of the various genera and species reported upon : — 



Class ASTEROIDEA. 

 Sub-Class Euasteroidea, Sladen. 



Order I. PHANEROZONIA, Sladen. 



Family Archasterid m. 



Sub-Family Archasteriism<:. 



Arrhaster angulatus, M. and T, 



