OPHIUBANS OF THE PHILIPPINE AND ADJACENT WATERS. 221 



rounded lobe (pi. 51, figs. 3, 4). In the specimen shown in figure 3 

 it is noticeable that two of the mouth shields are malformed; one 

 of them bears the madreporic pore, and it is not surprising that it 

 should be deformed; but its shape differs from that which I notice 

 on the specimen represented in figure 4, and it is especially devel- 

 oped obliquely toward the right anterior radius. Furthermore the 

 two adjacent adoral plates are smaller than the others, and are 

 widely separated from the median interradial line. The mouth 

 shield of the neighboring interradius also shows an abnormal out- 

 line; it is larger than the others, and its outline is asymmetrical. 

 The adoral plates, which are rather small, are triangular, broadened 

 outwardly, and terminate in a rounded angle ; they are not in con- 

 tact with each other in the median interradial line. The oral plates 

 tire high. The tooth papillae are very numerous, and within the two 

 lateral rows, which are very regular in arrangement, there may be 

 counted four and sometimes even five more or less irregular rows. 



The dorsal surface of the arms is flattened. The upper arm plates 

 are large, lozenge-shaped, very much broader than long, with the 

 proximal angle truncated and the distal angle rounded; the lateral 

 angles are rather sharp ; they are all in contact. The distal border 

 of these plates bears a variable number of small spinules which are 

 short, conical, and pointed. Toward the base of the arms these 

 spinules generally remain localized on the rounded distal angle of 

 the dorsal plates, from which they progressively extend over the 

 sides of these plates. 



The first under arm plate is small, square, with the angles and 

 the sides somewhat rounded; the proximal border is sometimes 

 slightly notched. The second plate is elongated, a little broader at 

 its distal extremity than proximally, with a narrow and straight 

 proximal border and a more or less convex distal border, which 

 sometimes resolves itself into two sides passing into each other over 

 an obtuse angle; the two lateral borders are divergent. The third 

 plate is almost as broad as long, with a rounded distal border and 

 slightly divergent sides. Beyond this the plates become markedly 

 broader than long, with the proximal border slightly concave and 

 shorter than the distal border, which is broadened and convex; the 

 lateral angles are much rounded. All these plates are in contact. 



The rather strongly projecting side arm plates bear very much 

 developed spines, of which the number may reach the figure eight 

 on the first segments ; but this figure falls very rapidly to six. The 

 length of these spines increases very rapidly from the first ventral 

 spine to the fourth ; the two following are the longest, and the last 

 dorsal spine is a little shorter than the preceding. The very rapid 

 increase in length which the arm spines show from the first ventral 

 upward, the second spine already sometimes attaining the length of 



