68 HAWAIIAN AND OTHER PACIFIC ECHINI. 



seem to be synonyms. The species which we recognize are lixula Linn, (in- 

 cluding jnistulum Leske, cequituberculala Bl. and australis Trosch.), from the 

 tropical Atlantic, ranging from the Mediterranean and Gulf of Guinea to 

 Brazil ; Dufresnii Bl. (including africana and alternans of Troschel), from 

 southern South America, Tristan d'Acunha, and West Africa ; pmictukda 

 Lamk., from the east coast of the United States and Mexico ; spatuligera Val. 

 (including grandinosa Val.), from Peru and Chili; and stellata Bl., from the 

 west coast of Mexico and Central America. All of these species are dis- 

 tinctly littoral, rarely occurring in depths exceeding 100 fathoms. 



In distinguishing the species of this genus, we find that no reliance can 

 be placed on the extent to which the interambulacra are covered by the 

 primary spines. Nor is this even an age character, for specimens of the 

 same size, of pundulata from Woods Hole and Newport, reveal the most 

 striking differences in this particular. The relation of the oculars to the 

 periproct, the number of primary tubercles on each coronal plate at the 

 ambitus, the sculpturing of the epistroma, and even, to some extent, the color 

 .and size, appear to furnish the best characters by which the species are to be 

 distinguished. The following table shows the characters revealed by the 

 species we recognize. 



Abactiual interradial areas, at least when cleaned, more or less distinctly 



gi'een DufrcsniL 



Abactinal interradial areas not at all green. 



Oculars large, usually 2, and often 3, in contact with periproct ; rarely in 

 small specimens there may be none fully insert; size large, li. d. 



usually 50-65 mm. and often up to 75 spatuligera. 



Oculars small, all distinctly exsert, or rarely one insert ; size moderate, 

 usually 30-45 mm., rarely up to 60. 



Primary tubercles numerous, 4-7 well-developed ones on each coronal 

 plate at ambitus in specimens over 30 mm. h. d. ; bare abactinal 



interambulacral spaces usually indistinct or wanting lixula. 



Primary tubercles fewer, seldom more than 3 well-developed ones 

 on a coronal plate at ambitus even in large specimens ; bare abac- 

 tinal interambulacral spaces usually more or less distinct. 



Plates of abactinal system and bare interambulacral areas so 

 finely granular as to have an almost velvety appearance, and 

 prettily marked with deep red in contrast to the gray or 



whitish ground color stellata. 



Plates of abactinal system and upper interambulacral plates 

 coarsely granular, not marked with deep red in contrast with 

 the ground color pmictulata. 



None of the species of this genus were taken by the "Albatross," but they 

 are included here in order that an account of their pedicellarioe may be given. 



