REPORT ON THE ASTEROIDEA. 331 



periphery in straight lines of great regularity, the bending of the furrows being sharp and 

 angular. 



The ambulacral furrows are slightly lanceolate in form, contracting as they approach 

 the actinostome, and again very gradually at the base of the ray as they proceed outward. 

 The tube-feet have a well-developed sucker disk. 



The terminal plate is squarely shield-shaped (pentagonal), its proximal extremity 

 angular, its sides subparallel and straight, and the distal extremity straight and truncate, 

 bearing two short robust conical spines directed horizontally in the direction of the pro- 

 longation of the ray. The breadth of the terminal plate is abruptly less than the breadth 

 of the ray at its attachment, which gives it the appearance of a superadded aftergrowth. 



Colour in alcohol, a bleached yellowish or ashy white. 



Locality. — Station 204. Off Tablas Island, Philippine group. November 2, 1874. 

 Lat. 12° 43' 0" N., long. 122° 9' 0" E. Depth 100 to 115 fathoms. Green mud. Sur- 

 face temperature 84° '0 Fahr. 



Subfamily Mimasteein^, Sladen, 1888. 



This subfamily includes only the single genus Mimaster, the morphological relations 

 of which are interesting as well as important. If the mind be allowed to indulge in 

 speculative deductions, the structure of Mimaster would appear to indicate a phylogenetic 

 line of descent which passes from the Archasteridse to the Pentagonasteridae, and has 

 branches to the Astropectinidse and Solasterida?, the lines of the series being indicated by 

 such forms as Leptopty chaster, Mimaster, Gnathaster, and Solaster. In our ignorance 

 of the developmental history of Mimaster, it is, however, premature to endeavour to 

 construct its genealogical tree with any pretension to accuracy ; and any such scheme as 

 that above suggested can only claim to be regarded as an exercise of the imagination. 



To confine our remarks to matters of fact, the mouth-plates, the actinal intermediate 

 plates, and the general form of Mimaster indicate an alliance with the Pentagonasteridae ; 

 whilst the more or less strongly marked representatives of the superambulacral plates, 

 the fan or oar-shaped lower end of the ambulacral plates, and the structure of the 

 abactinal plates, with their paxilliform developments, point to an affinity with the 

 Astropectinidae, Lcptop>tycliaster beiug the connecting form so far as the actinal inter- 

 mediate plates are concerned. 



Genus Mimaster, Sladen. 

 Mimaster, Sladen, Proc. Roy. Soc. Edin., 1882, vol. xi. p. 702 ; Trans. Roy. Soc. Edin., vol. xss., part ii., p. 579. 



Marginal contour stellato-pontngonal. Abactinal area subject to inflation. Actinal 

 area more or less convex. Abactinal floor composed entirely of independent paxillse, 



