NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 255 



arm. Oral shields wanting, except in one interradius. Under arm 

 plates numerous, forming an irregular pavement. No tentacle scales. 

 Arm spines reduced in number and size, with hooked tip. Genital 

 slit single in each interradius, just distal to adoral plates. 



Type-species. Ophioschiza monacantTia . 



This is one of the most remarkable ophiurans in the collection^ the 

 combination of a well-scaled disk, with the absence of upper arm 

 plates and oral shields and the presence of hooked arm spines being 

 most unusual, while the occurrence of a single genital slit in each 

 interbrachial space is certainly unique. The relationships of such a 

 strange form are most obscure but it is almost certain that it does not 

 belong here. The tips of the arms are spirally coiled as in Asteronyx 

 and its allies and I am in- 

 clined to think that Ophio- 

 schiza is probably one of the 

 Cladophiurae. 



OPHIOSCHIZA MONACANIHA, new 



species.a 



Disk 6 mm. in diameter; 

 arms about 20 mm. long. 

 Disk flat, covered with a 

 coat of coarse scales, of 

 which two in each interra- 

 dius are larger than the 

 others. Radial shields very 

 large, twice as long as broad, 

 separated from each other 

 by a narrow strip of small 

 scales. Upper arm plates 

 wanting save for one or 

 two rudimentary ones at 

 very base of arm. Inter- 

 brachial spaces below covered with bare skin but entirely sur- 

 rounded by coarse scales. Genital slit, short, oblong, placed trans- 

 versely in proximal angle of interbrachial space. Oral shields 

 wanting except in one interradius, where a rudimentary one much 

 wider than long lies proximal to genital slit. Adoral plates large 

 and distinct, hardly twice as long as wide, meeting broadly within; 

 oral plates moderate but oral tentacle pores very large. Oral 

 papillae rudimentary, three or four on a side. First under arm 

 plate large, pentagonal, longer than wide; succeeding plates broken 

 up into an irregular pavement, the component parts of which are 



FIG. 125. OPHIOSCHIZA MONACANTHA. x 9. a, FROM ABOVE; 

 6, FROM BELOW; c, SIDE VIEW OF TWO ARM JOINTS NEAR 



DISK. 



aM6vo signifying single, and &K.av6a, signifying spine, in reference to the single arm 

 spine. 



