THE OPHIURIDiE 



161 



32. Amphiura Diomedese n. sp 



Plate XII. ITigs. 1-7 



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Diameter of disk 14 mm. • width of arm close to disk, 2 mm. ; length of 

 arms, 7-8 times the diameter of the disk. Two mouth papilte on each side, 

 widely separated from those on the apex; they are usually equally large, 

 but sometimes the outer, sometimes the inner one is a little larger; the 

 outer is rounded, the inner more or less conical. Mouth shield with the 

 outer end somewhat restricted, an acute angle within, inner sides a little 

 re-enteringly curved or almost straight, side corners rounded, outer edge 

 straight. In the specimen figured they were wider than long; in some 

 specimens they are equally wide and long; in these latter the inner sides 

 are straight. Side mouth shields rather narrow, their outer end a little 

 broader than the inner end ; they just meet within. 



First ventral plate small, rounded, or five-sided. Those beyond a little 

 more broad than long (in Figure 1 they are wrongly represented as being 

 equally long and broad). The second and third have the inner end trun- 

 cated, those beyond have an angle within ; on the inner three-four joints 

 they are in mutual contact, then distinctly though not widely separated. 

 The outer edge is concave, outer corners slightly rounded; outer laterals 

 almost straight, inner a little re-enteringly curved. Side arm-plates with 

 spine-ridge little prominent ; the naked space separating the side plates 

 is rather small, not seen from the dorsal side. Dorsal plates more than 

 twice as broad as long, with a very obtuse angle within, and outer edge 

 slightly curved, rounding very abruptly at the sides; inner sides re-enter- 

 ingly curved. They are in contact until far out on the arm, but only the 

 first ones have the inner angle truncated. At the base of the arm are seen 

 one or more small, rudimentary dorsal plates. The arm is rather flat and 



broad, with a feeble keel above. 



The disk is covered with small, overlapping scales, among which the pri- 

 mary plates are distinct. The scales of the under side are smaller ; usually 

 they continue over the edge to the dorsal side, where they are very conspic- 

 uous, being directed opposite to those of the dorsal side. Usually there are 

 a few more conspicuous scales joining the mouth shield. The radial shields 

 are about as long as half the radius of the disk, wholly separated at the 

 • inner end by more small scales, at the outer end by a single row of larger 



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