126 DISCOVERY REPORTS 



and their indistinctness ; in the large number of abactinal and marginal pedicellariae ; in 

 the irregularity of the marginal plates, wholly covered with granules and lacking 

 characteristic tubercles. R 129 mm., r 43 mm., R = 3r; br 52 mm. (least distorted ray). 



Description. Perriers' description of H. hyadesi (Straits of Magellan, 326 m.) is 

 limited to a short comparison of the type with H. phrygiana} No figures were pub- 

 lished and so far as I am aware no second specimen has been taken. Perrier states, in 

 effect, that the only difference between hyadesi and phrygiana lies in the wider ambulacral 

 furrow of the former. In the adambulacral armature he finds slight differences but some 

 of these are covered by variations of phrvgiana. I have therefore assumed that the 

 characters of abactinal plates and marginal plates in respect to form, armature, and 

 occurrence of pedicellariae seemed to Perrier to be almost indentical in the two species. 

 As these features are radically different in H . falklandica I have considered it safe to use 

 for comparison a specimen of H. phrygiana (R 105 mm.) from 75 fathoms off Martha's 

 Vineyard, Massachusetts, which closely resembles Mortensen's figure^ of a Skagerrak 

 example. 



The following account of falklandica is largely in the form of a comparison with 

 heathi and phrygiana. It is hoped that the photographs may supply information on 

 details omitted or too summarily treated. 



Abactinal surface. The outlines of the plates are rather obscure and difficult to 

 distinguish on account of the crowded, unequal granulation, except in the case of 

 numerous oblong-elliptical primary plates. Almost the entire surface of these is occupied 

 by a long, low, bivalved (or trivalved) pedicellaria. On the border of these plates are 

 unequal low granules, very unequally spaced, or no granules at all. Smaller secondary 

 and tertiary plates usually carry a central globose prominent tubercle, occupying most 

 of the surface. Interspersed among these, as may be seen in the photograph, are 3 or 4 

 sizes of small tubercles and granules none of which clearly outline subcircularor irregular 

 secondary and tertiary plates as in phrygiana. In phrygiana the subcircular primary 

 plates generally carry a central thimble-shaped tubercle, the length of which seldom 

 exceeds the width of plate (but greatly exceeds it in H. spinosa Verrill of the north 

 Pacific). The rest of the surface is bare and periphery is bordered neatly by close-set, 

 small granules. In falklandica none of the plates show a bare surface, and therefore 

 greatly resemble H. heathi Fisher^ from 206 fathoms, Clarence Straits, Alaska, which I 

 am inclined to regard as a much closer relative than is phrygiana. Some of the abactinal 

 plates of heathi, however, carry prominent upright tubercular spines like those of 

 H. spinosa. 



Marginal plates. These are covered with unequal coarse granules and irregularly 

 placed short subglobose or acorn-shaped tubercles, with often a large bivalved pedi- 

 cellaria. Superomarginals 22 or 23, longer than wide except toward tip of ray where 

 they are wider than long and where a few plates have a bare surface. They are distinctly 

 smaller than in phrygiana and healhi and, partly due to granulation, are not sharply 

 differentiated from the abactinals. The (larger) specimen of phrygiana has only 16 



1 Perrier, 1891, p. 128. - Mortensen, 1933, pi. 11, fig. 2. 



^ Fisher, 1911, p. 231, pi. 44, figs, i, 2; pi. 58, figs. 5, 50; pi. 60, fig. 6. 



