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THE OPHIURIDiE. 



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irregularly placed, sometimes three rather large. The four to five teeth 

 are long, rounded, almost club-shaped, different from those in 0. seminttdus. 

 Mouth shield a little longer than wide, with a restriction at the outer end, 

 which thus looks almost like a little stalk. Side mouth shields rather long, 

 much broader without than within, where they just meet. 



First ventral plate of the same form as those beyond ; they are as 

 long as broad, with outer edge curved, inner end truncated; both inner 

 and outer laterals deeply re-enteringly curved, the latter on account 

 of the tentacle pores. The inner end of the ventral plates, especially 

 of those farther out on the arm, looks like a short stalk, and is some- 

 what elevated, making a keel along the median line of the arm. The 

 ventral plates are all in mutual contact and of the same form in the 

 whole length of the arm. The side arm-plates very broad and flat, with 

 outer edge sharp, rounded in outline ; from the tentacle pore to the mar- 

 gin of the arm runs a slight elevation, parallel to the outer edge of the 

 side-plate ; at the outer end of this elevation the arm-spines are inserted. 

 The dorsal plates are widely in contact in the whole length of the arm; they 

 are more than twice as broad as long, with a feeble keel. Inner and outer 

 edge curved, the former concave, the latter convex; the lateral sides straight. 

 Outer edge a little wider than the inner edge. One or two of the inner 

 dorsal plates mostly a little narrower than the rest, and there is then a little 

 naked space at each side of them. The arm is very flat and wide, lenticular 

 in cross section. The arm-joints enclosed in the disk are narrower than the 

 first free joints; farther out the arm again becomes narrower. The inner 

 part of the arm (3-4 first joints) rather deeply hollowed in the median line. 

 The disk is wholly covered : the inner part by a close granulation, 

 beneath which there are some indistinct scales, the outer part by the radial 

 shields and distinct small scales, the latter mostly covered with grains. The 

 naked radial shields are widely separated by one or more irregular rows of 

 scales ; they have the form of an almost rectangular triangle, about as long 

 as half the radius of the disk. In the interbrachial spaces the disk widens 

 a little, outside the radial shields. No marginal or primary plates. The 

 ventral side of the disk is covered on the outer part with rather distinct 

 overlapping scales, on the inner part with a close granulation, beneath which 

 the skin is almost naked. No genital scales distinct, no papillce along the 

 wide genital slits, which reach to the margin of the disk. 



Two arm-spines : the upper one about as long as a joint, the lower not 



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