CLARK: OPllIUKOIDEA. 441 



darker markings are chiefly apparent as transverse bands; the ann- 

 spines usually show spots or markings of dusky. As -^ rule, the arm- 

 spines of 0. hrcmpcs are shorter and less flattened than those of 0. 

 insulnria. 



Paumotu Islands: Makenio. Fakarava. 



Seventeen specimens. 



Ophiocoma erinaceus. 



Miiller and Troschel, 1842. Syst. Ast. p. 98. 



The specimens are all small, the largest having a disk only 15 mm. 

 across. 



Paumotu Islands: Makemo. Fakarava. 

 Seventeen specimens. 



Ophiocoma insularia. 

 Lyman, 1861. Proc. Boston soc. nat. hist., 8, p. 80. 



The specimens here listed as 0. insularia differ from 0. brevipcs 

 only in size, color, and arm-spines. They are from 10 to 22 mm. 

 across the disk, of very dark shades of brown, and with long, flattened 

 arm-spines. One specimen (from Papeete) is uniformly deep purplish 

 brown above and light wood-brown below. All the other specimens, 

 save one, have the arms more or less banded with dull yellowish on 

 the brown background, and even the disk may be variegated with dull 

 yellowish, or the specimens are variegated with light and dark shades 

 of brown. The one exception is from Easter Island and differs so 

 much from the other specimens that I propose to call it variety 

 longispina. In coloration it is uniformly blackish brown like 0. 

 erinaceus, but the granulations are very fine and the tentacle-scales 

 are narrow and pointed. It differs from typical 0. insularia in two 

 important particulars. The jaws are moderately long with very 

 evident oral plates, while in 0. insularia the jaws are very short and 

 wifle with almost no oral plates. The arm-spines of which there may 

 be five are exceedingly long and slender, 5-6 mm. long and equal to 

 four or fi\e arm-segments. As the arm-spines of Ophiocoma are 

 excessively varial)le and unreliable, this may be only an individual 

 peculiarity, but it profoundly affects the appearance of the specimen. 



Tahiti: Papeete. Three specimens. 



Easter Island. Twelve specimens. 



