MUSEUM OF COMPARATIVE ZOOLOGY, 123 
within, First under arm-plate triangular, with inner angle truncated, 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 curve ; 
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-papillw under the teeth is often wanting. 
Station 78, 1000 fathoms, 2 specimens. Station 146, 1375 fathoms, 12 + 
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 sides, standing at right angles to the axis; in 
the other the same plates are flat, and carry their spines on their owter 
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 far as 
aright anglo, instead of hugging the arm. Ophiozona illustrates this 
intermediate stage, while the third genus of the Ophiolepis groupe 
Ophioceramis —- may be said to bear its spines almost on the sides of 
the side arm-plates. As hinted above, O. obstricta and O. clausa differ 
in various ways from the typo, and are placed here waiting further in- 
formation. 
