62 C. F. Liitken on Ophiurans. 
opening appresele close to each other, on the outer side of the 
mouth-shield. Arm-spines mounted on a raised keel, and stand- 
ing boldly out from the arm. Upper edge of the disc, at the 
base of the arms, entire and without incision. 
Genus 1. Mouth-shields small, rounded, with a small, outward 
projection, separating the inner ends of the genital opening. On 
the back of the disc, traces of an incision at the base of each arm. 
Disc covered with moderate scales. Radial shields not large. 
Lateral mouth-shields within the mouth-shields proper. Below 
the — — broad, er tooth-papille. Upper arm-plates divi- 
ded in two. Two tentacle-scales. Three to four arm- spines. 
Species 0. gi 
Genus 2. Arms very see “ae thin. Disc with very small 
scales, = which some, near the edge, a little larger. Radial 
shields very small. Lateral — -shields on al: side of the 
mouth-shields proper. Upper arm-plates divided in three. One 
hree short a Species: O. reticulata, 
O. triloba, O. ‘Nereis 
Genus 3. Scales of the dise and radial shields rather small. 
No larger scales near edge of disc. Lateral mouth-shields within 
mouth-shields proper. ‘T'wo tentacle-scales. Upper arm-plates 
covered with many small scales. Species O. imbricata. 
Genus 4. Amphiura.—Disc with small, numerous scales, ar- 
ranged like tiles. Radial shields very distinct. An inward 
eurve of the disc, at the base of the arms, above. Mouth- shields 
small, not extending into the interbrachial spaces. Side mvuth- 
shields within the mouth-shields, eon broad, quadrangular. 
Arms extremely long and slender. poe arm- plates oval. Lower 
‘aed e, two, or no tentacle 
scales. an feeble, on a slight keel. Dis small. Six mouth- 
extending into esemnene “pene Side mouth-shields within 
the mouth-shields. Teeth very broad. Arms long and thick. 
Upper arm-plates surrounded by small scales. Lower arm-plates 
square. One foot-papilla. Arm-spines close set, the lower ones, 
at the tip of the arm, in form of double hooks. Mouth-papille 
six to each jaw, but none under the teeth. Side arm-plates like 
little ale Species O. aculeata. 
Genus 6. Ophiactis.—Disc ee as in openeed but on some 
of Sk Matic mee eteiceeeal! spin Arms five or six, rat 
short and thick. Teeth broad. One or two aia pantie to 
