OPIIIOCERAMIS JANUARII. 63 



lapping the second, wliich is the largest of all ; the space below the 

 tootii-papilU\3 is commonly vacant, but is sometimes occupied by two 

 very small niouth-pa])illa\ Tooth-papillce two ; narrow, long, and a 

 little curved, touching each other below, but diverging upwards, leaving 

 a ti'iangular space, which is filled )jy the lowest tooth* Teeth ten, 

 flattened, squarish, with a wavy cutting edge, which is re-enteringly 

 curved, and thickened at its middle point ; lowest one more or less 

 modified l)y the two tooth-papilla) ; the next four of even width, and 

 broader than the five uppermost ones. Mouth-shields rounded, about 

 as long as broad, Avith a curve within and a rounded angle without ; 

 length to breadth, 1.8 : 1.6. Side mouth-shields irregular, and very 

 small. Under arm-plates much broader than long, broader without 

 than Avithin ; outer and inner sides curved ; lateral sides strongly re- 

 enteringly curved ; outer corners prolonged laterally, as little peaks ; 

 length to breadth (eighth plate), 1.1 : 2.2 ; first plate very small, 

 rounded diamond-shape ; breadth 1""° ; towards the end of the arm the 

 plates become proportionately much longer, but the curves of their 

 sides remain about the same. Side arm-plates not encroaching above 

 or below ; considerably thickened along their outer edge, to afford a 

 base for the strong arm-spines. Upper arm-plates much broader than 

 long ; broader Avithout than Avithin, Avith outer corners Avell rounded ; 

 they are divided on the middle line into tAA'o quite distinct pieces, very 

 rarely into three or ca' en four pieces ; the Iavo or three first plates are 

 short and rudimentary, and are enclosed by the notch in the disk. Disk- 

 scales closely overlapping ; in the centre a circular, primary plate, 

 about l.y"""- in diameter ; four primary plates may be indistinctly seen 

 in each interbrachial, and three in each brachial space ; on the inter- 

 brachial spaces beloAV, the scales are narroAV, close, small, and even, 

 having an aAcrage length of about .7°""' ; at the base of each arm, 

 there are A-ery fnie scales, Avhich often run out a little Avay on the side 

 of the arm, much as in Ophiura. Arm-spines three (near base of arm, 

 sometimes four), stout, strongly tapering, rounded, a good deal flat- 

 tened ; middle one longest ; lengths to that of under arm-plate (thir- 

 teenth joint), l.T, 2.5, 2:1.1 ; the upper spine often is suddenly enlarged 

 at the base. Tentacle-scales small, rounded, flattened, a little longer 

 than broad, standing close together ; near the base of the arm there are 

 two outside and tAvo inside each pore ; but farther out the two outer 

 ones become smaller and smaller, and are soon reduced to a little edge, 

 lying along the lateral side of the under arm-plate. Color, in alcohol : 

 yellowish vandjke-brown, aboA'C ; below, the same, but lighter and more 

 yelloAvish. 



* These might almost as well be termed inon/Ji-papillcn, except that they do not lie quite on a 

 level with the rest. Tlie innermost papilhc in Amphiura are similar, but descend, so as to Ibrm 

 I)art of the I'ow of mouth-papilhe, among which they are included. 



