208 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



the second to the third, and then to those following, takes place in an 

 extremely rapid manner. In O. pentaphyllum, on the contrary, the 

 augmentation in the length of the spines takes place progressively, 

 as I showed in 1915, and as Russo described it in 1893. 



The armature of the disk and the rapid increase in the length of 

 the arm spines in O. aristulata, strongly recalls the conditions which 

 occurs in O. quinquemaculata Delle Chiaje 8 of the Mediterranean. 



I will add further that the general appearance of 0. aristulata is 

 very much more robust than that of 0. pentaphyllum, the arms are 

 thicker, stouter, and longer, and the arm spines are more developed. 

 These are the comparative differences. The coloration of O. aristu- 

 lata appears very uniform, the specimens being always of a light 

 color, grayish pink or pink, and they never show variations so ex- 

 tended over the whole gamut of colors as those known in O. penta- 

 phyllum. 



The type of O. aristulata was found by the Challenger in 34 S. 

 latitude and 18 E. longitude, at a depth of 274 meters (150 fathoms), 

 as well as at the entrance of Port Phillip in 69 meters (38 fathoms) 

 and in the Bay of Twofold in 219 meters (120 fathoms). The In- 

 vestigator found it among the Andaman Islands and on the coast of 

 Coromandel between 238 and 530 meters (130 and 290 fathoms). 

 H. L. Clark has recorded it from the coasts of Tasmania and of South 

 Australia at different depths between 119 and 366 meters (65 and 200 

 fathoms). 



OPHIOTHRIX ARMATA Kcehler. 



Plate 57, figs. 3-6 ; plate 97, fig. 2. 



Ophiothrix armata KCEHLEE ('05), p 103, pi. 10, figs. 1, 2. H. L. CLARK 

 ('15), p. 280. 



Locality. Celebes. 



One specimen (Cat. No. 41046, U.S.N.M.). 



Notes. I refer to Ophiothrix armata a very small specimen from 

 Celebes, of which the state of preservation leaves something to be de- 

 sired and in which the diameter of the disk scarcely exceeds 2.5 mm. 

 On plate 57, figure 5 I give a photograph of its dorsal surface. This 

 specimen differs only in its coloration from the type which I de- 

 scribed in 1905. The general coloration is gray with a few small dark 

 blue spots. Toward the distal angle of the radial shields there ap- 

 pears a very light band, bordered on each side by a dark blue line 

 which continues onto the median dorsal line of the arms; this band 



8 Ophiothrix quinquemaculata is the species which Russo in 1893 recorded under the 

 name of O. echinata, a synonymy which I erroneously adopted from him in my work of 

 1895 and which I have followed in all my later publications. It is sufficient to mention 

 the fact here in passing. I intend to return to it in the near future, in taking up again, 

 in more detail than I did in 1895, the study of the species of Ophiothrix of the European 

 seas, in order to describe in some detail the numerous variations which the armature of 

 their disks show. 



