ECHINODERMS OF CHALLENGER BANK, BERMUDA. 355 



mediate plates are wanting in nodosus, except on the actinal surface 

 of the disk, where there are a few; the lower surface of the arm is 

 covered chieifly by the inferomarginal plates, which abut directly on 

 the adambulacrals. The Bermudan specimens agree with nodosus 

 in this, and should, I think, be referred to that species, but it must be 

 admitted that they differ from both Perrier's description, and Verrill's 

 description and figures, of nodosum in their much smaller size and longer 

 and more slender rays. Perrier's type, from Guadeloupe, had R = 70 

 mm., while the specimens Verrill studied had R = 74 and 76 mm. 

 Sladen gives no measurements of his specimens from Bermuda, but 

 the largest of the six Museum specimens from the Challenger Bank 

 has R only 40 mm. These specimens have the ray only about a third 

 as wide at tips as at base, whils in the West Indian specimens it seems 

 to be as much as two-fifths. Verrill's figures show this, although his 

 description says the rays taper "to unusually slender tips." Perrier, 

 on the other hand, says the rays "termines en pointe tres-obtus." 

 Whether this difference in the form is constant and has any significance 

 can only be determined by actual comparison of specimens of the same 

 size. 



Sladen implies, but does not directly say, that some of the Chal- 

 lenger specimens lacked the "tubercular enlargements" character- 

 istic of nodosus. Of the specimens in the Museum of Comparative 

 Zoology collection, the three which are dried show these enlargements 

 plainly; in the smallest R = 34 mm.), there are 9, in the largest 

 (R = 40 mm.), about 25, and in the third specimen (R = 36 mm.), 

 about 35. The enlarged plates are all either abactinal or rarely super- 

 omarginal, and are chiefly on the basal half of the rays; they are only 

 rarely on the disk. They vary greatly in size and grade down to 

 normal plates. In the alcoholic specimens, they are much less con- 

 spicuous than in the dried ones, although the specimens are of about 

 the same size, and in one individual they seem to be ciuite wanting. 

 It seems probable that both in number and size the enlarged plates 

 increase with the age of the individual. 



Ophidiaster schismochilus^ sp. nov. 



Plate I. 



R = 113 mm.; r = 11 mm.; br = 16 mm.; R = lOr or 7br. 

 Disk very small and flat. Rays very unequal (113, 100, 90, 85, 55, 



2 crxicMa, a cleft -j-xfi^os, a lip or margin, in reference to the numerous pedi- 

 cellarian clefts on the margin of the ambulacral furrows. 



