320 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Ophiocoma brevipes varies especially in regard to its coloration, 

 which is sometimes very light and whitish gray, sometimes very dark 

 and almost black; certain individuals sometimes show very elegant 

 markings. Its characters appear more constant than those of O. 

 scolopendrina and O. erinaceus, with which this species is frequently 

 associated; but there are some variations in the number of the arm 

 spines on which certain authors have thought it possible to base dis- 

 tinct species, as, for example, O. ternispina Martens, which have not 

 been maintained. 



I shall speak here only of the variations in the form of the mouth 

 shields about which Loriol has already said a few words. Inde- 

 pendently of the outlines, which are sometimes angular, sometimes 

 rounded, these shields may be very much longer than broad, or on 

 the other hand as broad as long, and in the latter case they become 

 almost circular. The two photographs which I include, one of 

 the Philippine specimens (fig. 6) and the other of one from Mauritius 

 in my own collection (fig. 7) , show these two different forms ; in the 

 individual represented in figure 9 the form of the shield is inter- 

 mediate. 



The knowledge of these variations in the form of the mouth shields 

 appears to be of some importance, and possibly will permit of deter- 

 mining the degree of affinity that 0. brevispina and O. variegata, 

 species which Smith described from specimens from the island of 

 Rodriguez and which have not since been seen, have with O. brevipes. 

 These two forms are evidently very close to O. brevipes and perhaps 

 some day we shall be led to unite them with it, as Lyman has already 

 suggested ('82, p. 172) and as Jeffrey Bell appears to believe ('84, 

 p. 139). The mouth shields of 0. variegata have exactly the form 

 which is seen in O. brevipes, in which they are usually elongated. 

 In O. brevispina these shields are distinctly broader than long, a 

 form which I have never met with in 0. brevipes, but to which indi- 

 viduals such as those shown in figure 6 show an approach. The 

 question evidently can not be solved except by having at hand speci- 

 mens from Rodriguez. But the location of that island, which is very 

 close to Mauritius, and which is situated near 20° S. and 64° E., 

 renders very probable the presence of O. brevipes, the more so since 

 Smith recorded at the same time O. erinaoeus and Ophiomastix 

 venosa, species often associated with 0. brevipes. 



OpMocoma brevipes is widely distributed throughout the whole 

 Indo-Pacific region, and according to the record published by Ben- 

 ham it reaches as far as the Kermadec Islands. 



I have already mentioned that H. L. Clark ('14, pp. 291 and 359) 

 considered O. doderleini as a synonym of O. brevipes. Thanks to the 

 kindness of my excellent friend M. Bedot, director of the museum at 



