NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 175 



the specimens, but I can not suppress the feeling that there is some 

 mistake about the label "3702." If that were read "3102," a station 

 in 27 fathoms, off central California, the distribution of the species 

 would be quite natural. In view of the absence of Ophionereis, a 

 tropical and subtropical, littoral genus, north of California, it is hard 

 for me to believe that a Californian species occurs in Japan. I~srrall 

 therefore assume that 3702 is a mistake for 3102, at least until further 

 specimens are taken in Japanese waters. 



OPHIOCRASIS, new genus." 



Similar to Ophionereis, but with one or more secondary supple- 

 mental plates, just distal to the usual supplementary plates. Arms six 

 in young, five in adults. Reproduction by fission apparently occurs. 



Type-species OpJiiocrasis dictydisca. 



The presence of secondary supplemental plates is somewhat exag- 

 gerated in the drawings given herewith (figs. 79a, 79d 79</), for it is 

 almost impossible to represent them accurately, they are so small and 

 delicate. In Ophionereis the upper arm plates and their supple- 

 mentary plates, even in young and small specimens, are thick and 

 when dry are clear cut, with well-defined smooth margins. In 

 Ophiocrasis, however, when the arm is dried, it is seen that the upper 

 arm plates are thin, with a fairly well-defined distal margin ; the sup- 

 plementary plates have the margin very poorly defined and close to 

 them distally some additional minute plates are to be seen; of these 

 the one adjoining the upper arm plate is the most sharply defined; 

 the others are usually very hard to distinguish, and may be absent; 

 these secondary plates can only be seen when the arm is dry and are 

 best shown near the base of the arm. I have found nothing like 

 them in Ophionereis, though I have examined old and young speci- 

 mens of four species with great care. There seems little room for 

 doubt that reproduction takes place early in life by fission, as this is 

 clearly indicated by one specimen (see fig. 79^). At the same time I 

 am forced to the conclusion that the six-rayed condition is juvenile 

 and that the adult has only five rays. But it must be confessed that 

 a larger series of specimens is needed to determine these facts beyond 

 question. 



OPHIOCRASIS DICTYDISCA, new species.^ 



Disk 7 mm. in diameter; arms about 35 mm. long. Disk covered by 

 a delicate coat of very fine scales, coarser in the young and less em- 

 bedded in the skin than in the adult. Radial shields small, elongate, 



a ofaf, signifying snake, and Kpdate, signifying a compounding, in reference to the 

 compounding of the supplementary arm plates, and to be symphonious with other 

 ophiuran genera. 



b dlnrtjov, signifying net, and dlanoe, signifying disk, in reference to the reticulated 

 disk. 



