230 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



numerous, according to the individual. The club spines properly so 

 called maintain a rather regular length of from 0.25 Trim , to 0.30 mm. 

 in the large specimens; they are conical and usually bear three sub- 

 equal points. The longest club spines may attain and even surpass 

 1 mm. in length. Others are shorter. All transitional forms may be 

 observed (pi. 98, figs. 5a and o). The oval tentacle scale shows on its 

 free border a few short, conical, and pointed spines (fig. 5e) . 



OPHIOTHRIX EXPEDITA, var. RHABDOTA (H. L. Clark). 



Plate 31, fig. 5. 

 Ophiothrix rhabdoid H. L. Clark ('15), p. 278, pi. 13, fig. 4. 



Locality. — Marrougas ; shore ; from a coral head. 



Two specimens (Cat. No. E 340, U.S.N.M.). 



Philippines. 



One specimen (Cat. No. E. 363, U.S.N.M.). 



Notes. — One of the specimens is in a very fine state of preservation, 

 and the arms are almost all complete ; the diameter of the disk is 13 

 mm., and the arms are from 250 mm. to 300 mm. long. The other 

 specimen, which is a little smaller, is in rather poor condition; the 

 disk is deformed, and its dorsal surface is strongly wrinkled; the 

 arms are broken off at a rather short distance from their base. 



The dorsal surface of the disk is covered with small, short, slender, 

 and pointed spines, showing a certain number of conical and rather 

 strong teeth. In the midst of these spines are found small club spines 

 terminated by a few unequal and rather strong spinules; all inter- 

 mediate forms between the true spines and the club spines occur, ex- 

 actly as in the type. The club spines persist on the radial shields, 

 and, as they are not very closely crowded, the outlines of these shields 

 are easily visible. On the largest specimen they are rather large and 

 triangular; the internal border is slightly concave, the external bor- 

 der is rather strongly concave, while the third, or interradial, edge is 

 almost straight ; this last is markedly longer than the distal border ; 

 because of this the interradial angle is very close to the periphery of 

 the disk and lies almost at a level of one-third of the length of the 

 shields. In the other specimen the radial shields appear a little more 

 elongated, but the disk is deformed in such a way that the exact shape 

 of these shields can be ascertained only with difficulty. The photo- 

 graph of the dorsal surface of O. rhaodota published by H. L. Clark 

 (15, pi. 13, fig. 4) shows clearly enough the outlines of the radial 

 shields, and it seems to me that the form of these shields is close to 

 that which I describe, but the distal and interradial angle is a little 

 nearer the middle of the shield, without, however, being exactly at 

 the middle. 



I have described carefully the form of the radial shields in O. 

 rhaodota because I hoped that they would furnish characters which 



