94 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



broader than long. The under arm plates have at first the form 

 which I showed in the specimens from station 5450, but they become 

 relatively longer, and toward the extremity of the arms they are 

 twice as long as broad. The arm spines are five in number. 



To sum up, the only important difference between these specimens 

 and the two in good condition from station 5450, which, however, 

 is a difference sufficiently important to have caused me at first to 

 hesitate over their determination, is the presence of tentacle scales 

 on some of the segments at the base of the arm ; but I have been able 

 to convince myself that the presence of these scales is rather in- 

 constant. 



One of the specimens from station 5460 had the dorsal surface of 

 the disk completely torn away, and I have made a preparation of 

 it to show the characters of the peristomial plates; these are repre- 

 sented in figure 6 on plate 20. These plates, two in number, are 

 large and broad, each in the form of a right-angled triangle, a little 

 higher than broad, with the proximal border slightly concave and 

 the distal border convex ; the base of the triangle corresponds to the 

 median interradial line, along which may be made out the suture be- 

 tween the two adjacent plates. As a unit, these two plates recall 

 the structure which was represented by Lyman in Ophiochoeta 

 mixta, but in this species the two plates of each pair always remain 

 distinct. 



The individual from station 5505 is in very bad condition, and 

 the dorsal face of the disk is completely torn away; the disk must 

 have had a diameter of about 12 mm.; the arms are preserved for 

 a considerable length. On the parts of the dorsal surface of the 

 disk which are preserved, and on the ventral surface, there may be 

 made out an investment of very fine imbricated plates. Each of 

 the tentacle pores bears a small scale which is continued almost 

 throughout the length of the arms, but which is sometimes lacking, 

 doubtless on account of having been torn away. The mouth shields 

 are relatively large (fig. 2). 



The two specimens from station 5647 also have the disk in poor 

 condition, but their arms are mostly complete and well preserved; 

 the external appearance is absolutely identical with that of the two 

 specimens from station 5450, and like these latter they are of rather 

 large size; in one the diameter of the disk may reach 25 mm., and 

 in the other, which is larger, it certainly reaches 27 mm. ; the arms 

 are 95 mm. long. Like the preceding individuals, these two speci- 

 mens have tentacle scales on a certain number of the arm segments, 

 but here these scales are not very constant. They are always lack- 

 ing on the pores of the first pair, and they may be observed from 

 the pores of the second pair as far as those of about the seventh pair, 



