OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 171 



distal half which terminates in a rounded point; on the second and 

 third ventral spine the tip is slightly incurved, but strictly speaking 

 it does not form a hook. The surface of the first ventral spine and 

 of the last dorsal is simply rugose, but the others show narrow and 

 elongated teeth which are very closely crowded, especially in the 

 basal half of the spine, and principally along the proximal border, 

 and which disappear in the terminal part (pi. 96, fig. 9). 



The two tentacle scales are very small, equal, oval in form, and 

 stand at right angles to each other. 



The color of the specimen in alcohol is greenish, and rather light. 



Affinities and distinctive features. The species of the genus Am- 

 phioplus possessing two tentacle scales are very numerous, and in 

 general are very closely related to each other, though easy to dis- 

 tinguish. The new species can not be confused with any deep sea 

 form known from the Indian or Pacific Oceans. Amphioplus con- 

 ftnis Kcehler has the dorsal plates of the disk very large and the 

 mouth shields triangular; A. debilis (Kcehler) and A. firmus 

 (Kcehler) also have the dorsal plates of the disk rather large and 

 the mouth shields triangular; in A. depressus (Ljungman) the two 

 radial shields of each pair are in contact and the under arm plates 

 are very broad. Among the littoral species, A. causatus (Koehler), 

 A. cesareus (Koehler), A. conditus (Kcehler), A. hastatus (Ljung- 

 man), A. integer (Ljungman), A. intermedius (Kcehler), A. laevis 

 (Lyman). and A. praestans (Koehler) all have the radial shields 

 elongated and in contact except A. conditus in which the shields are 

 divergent, but that species possesses distinct primary plates and the 

 mouth shields have a very much elongated and pointed proximal 

 angle. The other species of Amphioplus differ greatly from the new 

 species, and it can not be confused with any of them. 



The majority of the species which I have just named possess only 

 three arm spines. Amphioplus rhadinobrachius H. L. Clark and A. 

 acanthinus H. L. Clark are also in this category, and, furthermore, 

 they differ from our species in numerous other characters. Amphi- 

 oplus lobatus Ljungman, from Sydney, New South Wales, is only 

 known from Ljungman's very short diagnosis; it possesses six arm 

 spines, but the terms "boucliers radiaux allonges," as well as " plaques 

 brachiales dorsales deux fois et demie plus larges que longues, 

 plaques brachiales ventrales a bord distal emargine," are characters 

 which do not apply to our species. A Japanese form which was 

 described by H. L. Clark under the name of A. lobatodes is perhaps 

 identical with A. lolatus (H. L. Clark, '15, p. 254, pi. 7, figs. 12, 13) ; 

 but A. legatus is very distinct from it, as may be seen by comparing 

 my photographs with those of H. L. Clark ; the mouth shields espe- 

 cially have a very different form, and the under arm plates, which are 

 as broad as long in A. lobatodes, are not narrow as in A. legatus. 



