326 HAWAIIAN AND OTHER PACIFIC ECHINI. 



with almost equal propriety, go in either one species or the other, are in the series 

 studied. As Mortensen has pointed out, the name " Amblypneustes ovum" 

 has been used very carelessly. It is borne on the original labels of more than 

 two thirds of our specimens of Holopneustes ! But typical examples of the true 

 ovum are easily determined. The status of grossularia is troublesome but it 

 is included in our table in accordance with the information given by Studer 

 and Mortensen. The latter seems to think it may not be an Amblypneustes 

 at all and this seems quite probable, but facts in support of the belief are want- 

 ing. It is very difficult to find tangible characters to distinguish it even as a 

 species and we are obliged to rely upon the peculiarities of the pedicellarke, as 

 given by Mortensen, though unable to find in them constant characters. It is 

 unfortunate that Mortensen does not include grossularia in his key to the 

 species of Amblypneustes, so that its really diagnostic features might be made 

 clear. The M. C. Z. specimens of formosus and pallidus appear to agree with 

 those in the Copenhagen Museum. 



In addition to the species already known, there are three others in the 

 M. C. Z. collection which appear to be undescribed, so that eight species are 

 distinguished in the following manner: - 



Ambulacra narrower than interambulacra; pore-pairs in distinct arcs of three. 



Spines red; coronal plates handsomely marked in median interambulacral area with 

 a broad zigzag, furrowed band, lighter colored than the lozenge-shaped areas 

 which separate its outer angles; poriferous areas usually light-colored .... formosus. 

 Spines not red; coronal plates not marked as above. 



Interambulacral plates high and few (18 in a specimen 20 mm. h. d.); second- 

 ary and miliary spines and tubercles very few; valves of ophicephalus pedi- 

 cellariae constricted near middle; those of triphyllous expanded at tip . . grossularia. 

 Interambulacral plates numerous (more than 20 in specimens 20 mm. h. d.); 

 secondary and miliary spines and tubercles more or less abundant; 

 valves of ophicephalous pedicellariae not specially constricted nor those 

 of triphyllous expanded at tip. 

 Vertical diameter more than .90 of horizontal; test usually ovoid and little 



flattened actinally. 



No secondary tubercles on interambulacral area between the two 

 vertical series of primaries but the area is crossed by a zigzag line 

 of miliary tubercles which connect the primary tubercles of oppo- 

 site sides; primary spines green, secondaries pale purple . . . pallidus. 

 Secondary tubercles common on interambulacra; no zigzag line of 



miliaries at all obvious ovum. 



Vertical diameter less than .90 of horizontal; test sphseroidal or depressed, 



more or less flattened actinally. 



Poriferous areas rather wide, the two together forming nearly or quite 

 half the ambulacrum. 



