320 bulletin: museum of comparative zoology. 



usually quite wanting, the bifid and trifid stumps forming a uniform 

 coat except on the radial shields which are more or less bare. But 

 in some specimens spinelets are present and in the holotype, these, 

 though few, are conspicuous because they are white in contrast with the 

 purple disk. The coloration of the holotype is as follows : — disk purple, 

 the outer margins of the radial shields and a few scattered spinelets, 

 white; arm-spines purplish at base but becoming reddish at tip; 

 upper arm-plates purplish, usually with the distal margin and a spot on 

 each side of the proximal end, whitish; upper ends of side arm-plates 

 also purplish with small markings of whitish; at intervals of one to 

 three segments, the upper arm-plate and adjoining portions of side 

 arm-plates are more or less red instead of purple; also at intervals 

 of two or three segments the white margin of the upper arm-plate is 

 wider; the general effect is that the arms are variegated with light 

 dull red, white and purple but rather evidently banded with the red; 

 under arm-plates with the sides purple, leaving a median stripe of 

 whitish running the length of the arm. In preservation, the red shades 

 are much decreased while the purple is deepened. Among the para- 

 types, there is much diversity of shade and of details of pattern but in 

 few specimens is there now any trace of reddish left; the banded 

 appearance of the arms persists very well however. In one specimen, 

 the disk was bright yellow in life, but is now nearly white. The 

 specimens collected at the Tortugas are distinctly lighter and redder 

 than those from Tobago and many show the white stripe on the 

 upper side of the arm more or less distinctly, at least near tip. 



Among the paratypes are two specimens of more than ordinary 

 interest. One is tetramerous; the disk is about 2 mm. across and 

 two adjoining arms are 16-18 mm. long; the other two arms are only 

 about 3 mm. long; there are four jaws; the specimen looks as though 

 it were the result of schizogonous reproduction. The other individual 

 is perfectly hexamerous; the disk is 5 mm. across and the arms about 

 25 mm. long. 



Ophiothrix brachyactis. 

 H. L. Clark, 1915. Mem. M. C. Z., 25, p. 269. 



It was a great pleasure to find this species living in the coralline 

 Algae in Buccoo Bay, Tobago, in April, 1916, but it is evidently not 

 common there, as only two specimens were taken. One of these is 

 smaller than the holotype but the other is a little larger, measuring 



