14 



THE VOYAGE OF H.M.S. CHALLENGER. 



plate just outside the true mouth shield. Two genitcal openings in each interbrachial space- 

 Pectinura is separated from Ophiopeza only by having a supplementary plate outside 

 the mouth shield ; and both are distinguished from OpUura by the minor anatomical char- 

 acter in this last, that, by a partial adhesion of the edges of the genital openings, each one 

 is divided into two. The similarity actually found in the skeletons would be expected. In 

 all three the disk is enclosed by a coat of stout imbricated scales and strong radial shields. 

 The genital plates, thick and rather wide, are attached to short, stout genital scales, 

 which, in OiMoj^eza and Pectinura are articulated farther inward, thus shortening the 

 genital opening. The mouth frames and jaws are strong and finely curved and bear three 

 thick peristomial pieces whereof two form an angle, whose opening outward is wedged by 

 the third. The arm Iwnes are of a high type, having thin wings, and the umbo, articu- 

 lating peg and other subordinate parts well marked. 



Disk cov- 

 ered, under 

 its granula- 

 tion, with- 

 coarse scales 

 or swollen 

 plates. 



No pores between _ 

 under arm plates. 



Table of Species of Pectimira. 



'Radial shields granulated. 13-15 arm spines, 

 Eadial shields granulated. 9 short arm spines. 



Disk, under 

 its gi-anula- 

 tion, cover- 

 ed with 

 minute and 

 smooth 

 scales. 



Pores between first 

 and second under 

 arm plates. 



Ten thin equal arm 

 spines ; underarm 

 plates encroached 

 on by side arm 

 plates, . 



Pores only between 

 first and second 

 imder arm plates, 



Pores between the 

 under arm plates 

 continued for 

 some distance 

 along the arm, . 



Of doubtful place, 



Eadial shields naked ; also some other disk 

 plates. 9 arm spines, 



Radial shields naked. 3 arm spines, . 



' Arms cylindrical at their insertion in the disk, 

 which is puffed, .... 



Arms widened at their in- 1 10-11 arm spines, 

 sertion in the disk, which V 

 is fiat, . . ) 5-6 arm spines, . 



7-8 conical arm spines, the lowest one a little 



the longest, 



Pectinura sjrhiosa. 

 Pectinura arenosa. 



> Pectinura infernalis. 

 Pectinura heros. 



> Pectinura gorgonia. 



Pectinura marmorata. 

 Pectinura i<tellata. 



Pectinura vestita. 



Pectinura macidata. 

 \ Pectimira septemqiinosa. 



8-9 flat, pointed arm spines, the lowest one 

 very long and flat, often equal to two joints 



in length, 



> Pectinura riaic, 



'tjida. 



Pectinura verrucosa. 



