OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 435 



which I have already described the characters. The plates of the 

 dorsal surface of the disk are arranged more irregularly and the 

 diiference in size between the largest and the smallest is less marked. 

 These differences have no great importance. 



The surface of the upper arm plates in O. irregularis is not plane, 

 but is raised up very markedly toward the distal border, as may be 

 appreciated from the lateral view of the arm which I give in plate 

 SO as figure 1. There is no large rounded tubercle like that observ- 

 able in O. nodosa Duncan or O. rugosa Kcehler; there is a thickening 

 of the whole distal portion of the plate which can not be compared 

 with the projecting rounded and clearly defined tubercle which oc- 

 curs in the last two species; in these the upper arm plates are very 

 much narrower than in O. irregularis. 



I notice that the majority of the tentacle pores have, in addition 

 to the two well-known scales, a very small supplementary scale situ- 

 ated toward the proximal border of the pore. There may also be 

 some irregularities in the arrangement of the scales; thus some- 

 times this supplementary scale reaches a rather large size, while the 

 two normal scales become smaller, so that there are three subequal 

 scales. This peculiarity has already been described by Duncan in 

 O. nodosa,' I do not believe that this constitutes an important spe- 

 cific character. The same feature has also been described by Lyman 

 in O. elegans, and I find it also in other species, for example, in O. 

 affinis Studer; it may be recognized in the photographs which I 

 published of these two species in 1914 (see Kcehler '14a, pi. 9, figs. 

 16, 18), but the outlines of the tentacle scales are not very distinct, 

 for the plates have suffered somewhat in reproduction. I notice 

 traces of this third scale in 0. ctncta Muller and Troschel, but it is 

 here less developed than in the species which I have just cited. 



The dorsal surface of the body shows an orange coloration, which 

 is very pronounced, especially in the central region of the disk, 

 surrounded by a broad black circle with an irregular contour; the 

 arms are ringed with black. The ventral surface is grayish white 

 studded with numerous small light orange spots. 



OPHIOPLOCUS IMBRICATUS (Muller and Troschel). 



See for bibliography: 



Ophioplocus imlricatus Kcehler ('05), p. 18; ('07), p. 288; ('07b), p. 

 243.— H. L. Clabk ('08), p. 289; ('11), p. 30; ('15), p. 344; ('15a), p. 

 89.— Matsumoto ('17), p. 301, fig. S3. 



Localities. — Albatross station 5212; east of Masbate; Panalangan 

 Point bearing S. 54° 30' E., 26.87 kilometers (14.5 miles) distant 



