MUSEUM OF COMPARATIVE ZOOLOGY. 123 



within, Fii"st under ann-plate triangular, with inner angle truncateJ, lateral 

 sides re-enteringly curved, and outer edge rounded ; the rest are narrow and 

 rudely pentagonal, those near base of arm having the inner angle truncated, and 

 the outer slightly curved ; inner laterals bounded by a re-entering curvfi ; 

 length to breadth .8 : .8. Side arm-plates broad and flat, not meeting below, 

 separated above by the broad upper arm-plates, which are much wider than' 

 long, and cover the whole upper surface of arm, having the lateral sides nearly 

 straight, and edge with a slightly re-entering curve. Disk flat and round ; 

 central portion covered with a thin, naked, cross-wrinkled skin ; along the 

 margin are minute scattered granules, which, with the thick skin, hide the 

 underlying scales. Radial shields longer than broad, much rounded, widely 

 separated ; length to breadth 2 : 1.5. Lower interbrachial space covered with 

 a thin skin, on which there is a very scattered granulation. Genital openings 

 wide, extending from mouth-shield to edge of disk. Genital scale not seen. 

 Three small, tapering, cylindrical arm-spines, less than half as long as an arm- 

 joint, set low on the outer edge of side arm-plate. Two small rounded scales 

 on the interbrachial edge of each tentacle-pore. Color in alcohol, greenish- 

 gray. 



This species grows to a large size ; one with a disk of 20 mm. was similar to 

 the above, except that the mouth-angle was narrower and more prolonged, and 

 bore, on each side of the mouth-frames, eight small, very close-set papilla). 

 The granulation -of the disk was feeble ; in many specimens it is wholly want- 

 ing. The pair of small mouth-papillae under the teeth is often wanting. 



Station 78, 1000 fathoms, 2 specimens. Station 146, 1375 fathoms, 12 -f 

 specimens. Station 156, 1975 fathoms, 1 specimen. 



It is with doubt that the two following species are referred to 

 Ophioceramis. They are both rather young, and have perhaps not 

 taken on their full characters. Dr. Liitken pointed out the two divis- 

 ions of Ophiurans, in one of which the side arm-plates, rising in ridges, 

 bear the spines on their sidesi, standing at right angles to the axis ; in 

 the other the same plates are flat, and carry their spines on their outer 

 edge parallel with the axis. Ophiothrix is an exact type of the first, 

 Ophiolepis of the second. But there are genera intermediate, where the 

 base of the spine, not crowded against the side arm-plate, as in Ophiolepis, 

 stands on the outer corner of the edge, and has a lateral motion as fur as 

 a right angle, instead of hugging the arm. Ophiozona illustrates this 

 intermediate stage, while the third genus of the Opthiolepis group — 

 Ophioceramis — may be said to bear its spines almost on the sides of 

 the side arm-plates. As liinted above, 0. ohstricta and 0. claum differ 

 in various ways from the type, and are placed here waiting further in- 

 formation. 



