NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 47 



v The range of kinbergi extends from the Gulf of Tokyo to the Red 

 Sea and New South Wales, while liiikeni ranges from Alaska to San 

 Diego, California. The two are thus very evidently warm-water 

 species, found only in comparatively shallow water. They are there- 

 fore widely separated from each other, but the range of sarsii broadly 

 overlaps that of each of them, so that sarsii and Jcinbergi may both 

 be found on the coast of Honshu Island, Japan, while sarsii and lut- 

 Iceni are both common off the coast of Oregon and Washington. The 

 three species are easily distinguished as follows: 



KEY TO SPECIES. 



Arm comb made up of short, broad, truncate papillae, which are closely crowded side 



by side, so that there is no resemblance to a comb lutkeni. 



Arm comb made up of well-spaced, blunt or pointed papillae, so that there is more 

 or less resemblance to a comb. 



Disk scales variable; more or less irregular, and angular, often somewhat swollen; 

 primary plates rarely noticeable; comb-papillae short and bead-like or more 

 or less elongated, the length not often exceeding three times the greatest thick- 

 ness; middle arm spine becoming the longest at tip of arm sarsii. 



Disk scales flat, the primary plates conspicuous and usually surrounded by belts 

 of smaller ones much as in Ophiolepis; comb-papillae very slender, their length 

 at least five times their thickness; middle arm spine becoming the shortest at 

 tip of arm Iciribergi. 



OPHIURA MICRACANTHA, new species.o 



Disk 12 mm. in diameter; arms about 50 mm. long. Disk covered 

 by several hundred overlapping scales, of varying size, among which 

 the centro-dorsal and several radial and interradial plates can be dis- 

 tinguished by their larger size. Radial shields about as wide as long, 

 separated, or barely in contact at middle, outer ends rounded, inner 

 somewhat pointed. Basal upper arm plates much wider than long, 

 tetragonal, distal side longest and distinctly convex; gradually the 

 plates become longer and narrower, until at middle of arm they are 

 longer than wide and are very narrow proximally; they remain in 

 contact nearly to tip of arm ; in small specimens (disk diameter about 

 8 mm.) only first two or three plates are wider than long. Inter- 

 brachial spaces below covered by numerous scales, of which those 

 nearest margin are largest. Oral shields pentagonal, wider than long, 

 with a slight notch in lateral margins at end of genital slits. Adoral 

 plates long and slender, three or four times as long as wide ; oral plates 

 shorter and stouter. Oral papillae three on each side, wide, two outer 

 ones with a thin sharp edge which is often distinctly notched. Teeth 

 about four, lowermost smallest. Genital slits long but not conspicu- 

 ous. Genital scales hidden by scaling of interbrachial spaces, but 



McKpbe, signifying small, and aKavOa, signifying spine, in reference to the very 

 small, middle arm spine. 



