. Bulletin - United States National Museum. Science. NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 255 arm. Oral shields wanting, except in one inteiradius. 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.—OphioscJiiza monacantha. 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
. Bulletin - United States National Museum. Science. NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 255 arm. Oral shields wanting, except in one inteiradius. 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.—OphioscJiiza monacantha. 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 mAsteronyx and its allies and I am in- clined to think that OpJiio- scJiiza is probably one of the Cladophiurse. OPHIOSCHIZA MONACANTHA, new ; 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 Fig. 125.—Ophioschiza monacantha. X!>. a, from above; two rudimentarv ones at ^' ^^^^^ below; c, side \7ew of two arm joints near very base of arm. Inter- brachial spaces below covered with bare skin but entirel}^ 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 A^er}' large. Oral papillae rudimentary, three or four on
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