AMBLYPNEUSTES TRISERIATUS. 331 



distinguish them at a glance from griseus, while they are equally different from 

 the specimens of pachistus which came with them. The very narrow poriferous 

 areas, the peculiarities of the tuberculation and the color combine to make 

 them representatives of an undescribed species. Among the specimens in the 

 M. C. Z. collection, received from the "Challenger" material as A. formosus 

 and taken in Bass Strait, 38^40 fms., are two which seem to be the young 

 of grandis. One is 22 mm. in diameter and except for the fact that it is 

 much lighter colored and has the dull rose markings more distinctly indicated, 

 it resembles the larger specimens quite closely; the pair of miliaries above each 

 of the outer ambulacral primaries is noticeable; the primary spines are white, 

 but of course they may have become bleached with the passing of forty years. 

 The other specimen is only 16 mm. in diameter and is quite possibly not grandis; 

 the narrow poriferous areas and the tuberculation of the ambulacra are charac- 

 teristic but the coloration is peculiar, for the test has a dull greenish cast and the 

 large spines are bright green with white tips. 



Amblypneustes triseriatus, 1 sp. nov. 

 Plates 104, fig. 5; 112, fig. 5. 



The specimen upon which this new species is based is a bare test without 

 actinostomal membrane or abactinal system, but so unique in the characters 

 it shows that it is without doubt specifically distinct from any described Amblyp- 

 neustes. This test is 30 mm. in diameter and 26 mm. high, with the actino- 

 stome 11 mm. in diameter and the abactinal system (wanting) 6.5 mm. across. 

 There are 28 interambulacral, and 43 ambulacral plates in each column. The 

 ambulacra (PL 104, fig. 5) are 9.5 mm. wide at the ambitus, while the interambul- 

 acra are scarcely 9, so that the former are obviously the wider. The two porif- 

 erous areas together are about equal in width to the interporiferous space. The 

 pores are small and the pore-pairs are so uniformly arranged and the arcs are so 

 nearly horizontal that each poriferous area shows three distinct vertical series of 

 pore-pairs. Corresponding to these but much more irregular and imperfect are 

 three vertical series of miliary tubercles. Of these tubercles those just within 

 and below the middle pair of pores are the largest. Each interambulacral plate 

 at the ambitus bears a primary tubercle, a little outside of the centre, the areola 

 of which occupies scarcely one half the height of the plate. On the outer end 

 of the plate is a secondary tubercle (or often there are two) and on the inner half, 



1 triseriatus = in three series. 



