270 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Notes. I refer numerous specimens to OpJiiothrix stelligera, of 

 which the Albatross has collected a very fine and very interesting 

 series showing the very considerable variations to which this species 

 is subject, especially in regard to the armature of the dorsal surface 

 of the disk, as may be seen by comparing my photographs on plate 

 53, figures 2, 3, with those on plate 55, figures 1, 4, showing the ex- 

 tremes of which the intermediate types are represented in various 

 figures on plates 53-56. I have thought it well to include photo- 

 graphs of a rather large number of specimens in order to facilitate 

 the determination of this species which is not always easy to recog- 

 nize because of its variations. The coloration also shows rather 

 considerable differences. 



As was determined by Lyman, Ophiothrix stelligera is especially 

 characterized by having the dorsal surface of the disk covered with 

 club spines ending in a crown of five or six slightly divergent and 

 very regular spinules, an arrangement to which the species owes its 

 name ; these club spines may pass over onto the radial shields, where 

 they are usually less closely crowded than on the rest of the disk, 

 and true spines may occur among them. The arrangement of the 

 arm spines and the shape of the upper and under arm plates have 

 been described by Lyman, by Doderlein, and by myself (see Kcehler 

 '05, p. 87). I am figuring a certain number of individuals in which 

 the dorsal surface is covered exclusively with club spines, coming 

 from the following stations: Station 5142 (pi. 54, fig. 3); station 

 5145 (pi. 54, figs. 1, 2) ; station 5146 (pi. 56, fig. 7) ; station 5147 

 (pi. 53, fig. 2) ; and " Philippines" (pi. 53, fig. 4). These examples 

 are quite typical. The same is true of numerous others in which true 

 spines, which are usually rather rare, are intermixed with the club 

 spines; of this type are the specimens from stations 5146 (pi. 55, 

 fig. 3) and 5147 (pi. 53, fig. 5, and pi. 56, fig. 4). In all these speci- 

 mens the - few true spines are relatively little developed, remaining 

 slender and rather short. But in others these spines may be more 

 developed, either in numbers or in dimensions; this occurs for ex- 

 ample in the specimen from station 5141 (pi. 54, figs. 4, 5), and espe- 

 cially in those from station 5144 (pi. 55, figs. 1, 2), in which these 

 spines are very numerous and very stout, and are provided with very 

 evident denticulations. The covering formed by these spines gives 

 the disk an appearance very different from that which is usually 

 seen in O. stelligera. It does not seem to me possible, however, to 

 separate these specimens specifically from those in which the spines 

 are smaller and less numerous, or even completely lacking, for I find 

 all possible intermediates. The radial shields may also show rathei 

 important variations, both in their size and in their covering ; some- 

 times they are covered with club spines almost as closely placed as^ 



