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134 



THE OPHIURIDiE. 



Numerous specimens from Stations 3362^ 1175 f.; 3363, 978 1; 3366, 

 1067 f. ; 3374, 1823 f. ; 3376, 1132 f. ; 3381, 1772 f. ; 3382, 1793 f. ; 3392, 

 1270 f. ; 3399, 1740 f. ; 3400, 1322 f. ; 3414, 2232 f. ; 3431, 995 f . 



Younger specimens differ in having the radial shields separated by only 

 a single row of scales ; the primary plates are distinct. The genital slits 

 only reach to the second joint, and there are only 4-6 arm-spines. 



The larger specimens do not vary to any great extent. The mouth shield 

 sometimes is divided by a transverse line, and also in general outline it is 

 rather variable. The arm-spines sometimes are shorter and thicker. Some- 

 times there are a few small spines along the margin of the disk. There is a 

 rather thick skin over the disk scales, which are not hidden by it, the skin 

 being translucent. 



20. Ophiomusium Diomedese n. sp 



Plate IV. Figs. 1-3. 



Diameter of disk, 13 mm. ; width of arm close to disk, 2.5 mm.; length 

 of arms unknown. 7-8 mouth papillae to each side : the three outermost 

 ones are rather long, closely soldered together, somewhat rounded; the 

 four-five innermost ones are shorter, more pointed, and not close set ; one 

 pointed on apex of jaw. Mouth shield small, spearhead-shaped, with outer 

 edire straio-ht; a httle lono;er than broad. Side mouth shields with outer 

 end broad, inner end somewhat narrower ; meeting within. 



First ventral plate very small, polygonal. All ventral plates with outer 

 edge straight ; the three-four first are in mutual contact, the second and 

 third having their inner end truncated ; second to fourth have the lateral 

 edges rather deeply constricted by the tentacle pores ; from the fifth they 

 are triangular, widely separated ; they continue to the end of the arm (as 

 far as can be judged, all the arms being broken). Side arm-plates with 

 outer edge rather prominent, thick, rounded ; meeting below from the fourth, 

 above from the second joint. Dorsal plates triangular, their outer edge 

 almost straight, only with a little peak in the median line ; the first dorsal 

 plate has inner end truncated. At the arm-basis there are some rudimen- 

 tary, irregular polygonal dorsal plates, and at the sides (outside the radial 

 shields) there are, corresponding to these dorsal plates, some plates, which 

 look like rudimentary side arm-plates, but are not so really. Arms flat 

 above and below. 



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