146 OPHIONEREIS XANTUSIL 



plate), .5 : .4. Upper arm-plates triangular, with a rounded angle 

 directed outward, and a sharp angle directed towards each side ; 

 length to breadth (eleventh plate), .5 : .9. Supplementary pieces as 

 long as the joints, triangular, with outer side curved ; near the end of 

 the arm they become proportionately smaller, and the upper arm-plates 

 gradually take on a more hexagonal shape. Disk-scales very close and 

 fine, about 200 to a square mm. Radial shields very small and narrow, 

 about .T""""' long. The usual comb of papilla3 along the edges of the 

 genital slits is not much developed. Arm-spines rather short, flattened, 

 and cut off square at the end ; middle one longest ; lengths to that of 

 under arm-plate (seventeenth joint), .7, 1.2, .9 : .r5. Tentacle-scale large, 

 round, thin ; length to that of under arm-plate, .3 : .5. Color, in alcohol : 

 above, disk faint greenish-gray, finely lined with Ijrownish ; above the 

 base of each arm a dark-purple fork, of two converging lines ; some- 

 times a few other veins of dark purple ; arms brownish straw-color, 

 with a fiiint, broken line of whitish running lengthwise ; at intervals 

 of from five to twelve joints, a dark purple joint, making a cross 

 band ; below, interbrachial spaces same as upper surface ; other parts 

 lio-ht straw-color. 



Vcu^iations. — The color seems pretty uniform ; the dark markings 

 at the base of the arms may differ somewhat in shape and size, and the 

 arm bands may either go entirely round, or be confined to the upper 

 surface. A small specimen, with a disk of 4.2""°-, had arms of 22'"™-. 

 The number of disk-scales to a square mm. was al^out the same as in 

 larger ones. The lower arm-plates were longer, and more concave on 

 their lateral sides ; the teeth had all round cutting edges ; the spines 

 were more rounded and tapering than in the adult ; length of the long- 

 est to that of under arm-plate, .5 : .3 ; the radial shields could hardly 

 be distinguished. The mouth-shields vary a little in being more or less 

 rounded. 



0. Xantusii differs from 0. annulata in having shorter and blunter 

 arm-spines, and shorter arms ; the color is also different ; — from 0. 

 reticulata, in blunter arm-spines, shorter arms, and a different pattern 

 of color. 



