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THE OPIIIURID^. 



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specimens^ not on the small ones- they are widely separated above almost 

 to the end of the arm. The dorsal plates are short and very broad, roof- 

 sliaped, outer edge somewhat concave; they are in contact in almost their 

 whole breadth; farther out they become narrower, more elongated. In the 

 rather deep incisure of the disk are seen 3-4 dorsal plates, not very rudi- 

 mentary. The arms are very high on the dorsal side, flat on the ventral 

 side, almost triangular in cross section. 



Disk covered with rather small, but thick and swollen scales- on the 

 central part only some few of the scales are swollen, towards the marcnn 

 they are all so. Primary 2:)lates inconspicuous. Eadial shields rather small 

 but also thick and swollen, therefore very conspicuous; they are almost e""^- 

 shaped, widely separated by several irregularly arranged thick scales. No 

 large marginal plate in the interbrachial spaces. Ventral side of the disk 

 covered with similar thick scales, though not quite so large as those on the 

 dorsal side. Edge of the disk rounded. Genital plates small, distinct only at 

 the outer part of the disk; they do not extend far upwards to the dorsal side 

 of the arm, only to the outer corner of the radial shields; the arm-comb there- 

 fore is very inconspit^uous, far from reaching the median line at the arm- 

 basis; only 4-5 papillae to be seen from the dorsal side. PapilljB alon 



g the 



genital slits well developed, close set; at the inner end of the slits they are 

 irregularly pointed, farther out they become more square, as are the papilla) 

 of the arm-comb. Usually they are somewhat thickened at their basis. 

 There is no secondary arm-comb, though sometimes there are one or two 

 small papillro between the end of the side arm-plate and the dorsal plate. 

 Three small arm-spines, the two lower ones rather close together, the 

 upper one apart, not distinctly longer than the other. The outer edrre of 



to 



the side arm-plate is somewhat curved outwards between the two upper 

 spines; Figure 13 does not give that well. Tentacle pores of the inner part 

 of the arm large and conspicuous, farther out they rapidly diminish in size • 

 from c. 10th joint they are quite rudimentary (or wanting), but one tentacle 

 scale continues almost to the end of the arm. First pair of pores apparently 

 opening into the mouth space, but in fact it is separated from it by the out- 

 ermost mouth papilte ; c. 8 tentacle scales on each side. The second pair 

 has 5-6 on inner, 6-7 on outer side, and then the number of scales gradu- 

 ally diminishes; from about the tenth joint there is only one scale on the 

 outer side, none on the inner side. 



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At the outer end of each pore there lies a little but distinct plate, which 



