244 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



and Troschel's type, and that the real characters of this latter species 

 completely eluded him, as has been the case also with other authors 

 (see Kcehler, '04a, p. 105). 



To H. L. Clark belongs the credit of having clearly established the 

 characters of O. koreana, and especially of having shown the very 

 great variations which this species may show, principally in regard 

 to the armature of the dorsal surface of the disk. He was able to 

 examine a very considerable series of specimens, 411 in all, which 

 were collected in the Japanese seas at depths between 11.5 and 302 

 fathoms. I refer the reader to the memoir of this American natural- 

 ist for the description of the principal variations which he has ascer- 

 tained ('11, p. 257 and following pages). 



The specimens which have been sent to me also show variations, 

 but these are less extensive than those of the specimens studied by H. 

 L. Clark ; it is true that my collection is less extensive than his. The 

 majority of the specimens agree with that from station 5116, of which 

 I give two photographs (pi. 45, figs. 2, 3). The dorsal surface of the 

 disk is uniformly covered with club spines terminated by three long 

 divergent spinules, identical with those which H. L. Clark has repre- 

 sented ('11, fig. 128a), and of which I give a few photographs; some- 

 times these club spines bear four points, or more rarely two only; 

 but in general they show a great regularity (pi. 94, fig. 4a). The 

 very large radial shields are always more or less covered with club 

 spines. Such are the characters which the individuals from stations 

 5135, 5179, 5212, 5265, 5391, 5392, and 5421 present ; in those from 

 station 5257 the radial shields are almost naked ; in the other speci- 

 mens, these shields, which are almost entirely naked, become rela- 

 tively still larger, as may be seen in the specimens from stations 5187 

 and 5373, of which I give photographs (pi. 45, figs. 4, 5), and on that 

 from station 5541; in the specimen from station 5221 the radial 

 shields which are similar to those of the preceding in dimensions, bear 

 a certain number of club spines. In the specimens which I have just 

 mentioned, with the exception of that from station 5187, the dorsal 

 surface of the disk carries only trifid or sometimes quadrified club 

 spines, but these club spines may elongate and transform into small 

 true spines. This transformation may be easily followed in the speci- 

 men from station 5179, in which the central region of the disk shows 

 typical club spines Avhich elongate little by little toward the periph- 

 ery and become transformed into very elongated, thin, and rather 

 slender true spines, furnished with denticulations throughout their 

 length (pi. 45, fig. 1). The indivdual from station 5213, on the other 

 hand, bears club spines in the peripheral part of the disk, and these 

 elongate little by little in the central region to form eventually true 

 spines, which are, however, very much less developed than in the 



