32 EXPLANATION OF THE PLATES. 



PLATE II. 



Ophiacantha stellata, Figs. 16-18. Fig. IG, "jO, under surface. The difference between 

 the second and third under arm-plates is to be noted. Just outside the second small spine of 

 the second plate (on the arm to the right of the observer) may be seen protruding the minute 

 tentacle. Fig. 17, ^, upper surface, showing the small, deeply indented disk and the peculiar 

 side arm-plates, constricted between the joints, and rising suddenly into a ridge for the arm- 

 spines. These characters, and the narrow, nearly covered radial shields, ai-e those of the 

 typical 0. setosa, from which so many species now referred to the gemis vary. Fig. 18, f, three 

 joints, seen from above, to show their characteristic form. 



Ophiacantha hirsuta, Figs. 21-23. Fig. 21, J-j)-, under surface, with the unusually long 

 jaws, large mouth-tentacles, and the first under arm-plate partly rolled on itself Fig. 22, Y-, 

 upper surfiice, showing the numerous fine spines. Fig. 2.3, -Sj-"-, the lowest arm-spine, to exhibit 

 the peculiar thorns of its point and edges. 



Ophiomitra cervicornis, Figs. 19-20, f. Fig. 19, under surface. The first under 

 arm-plate is folded on itself, and the small mouth-tentacle of the second pair protrudes between 

 it and the outer corner of the side mouth-shield. On the under arm-plates, beyond, the tentacle- 

 scales have, first, the shape of thorny crescents, and then of little lobes. Fig. 20, upper surface, 

 showing the large radial shields and the coarse spines and stumps of the disk. 



Ophioplax Ljungmani, Figs. 24, 25, f . Fig. 24, upper surface ; the scales of the margin 

 are covered by a minute granulation. Fig. 25, under surface, showing the singular oval tentacle- 

 scale, with three or four miuute ones on the under arm-plate. The interbrachial space is finely 

 granulated. 



PLATE III. 



Amphiura anomala, Figs. 26 - 28, -V-. Fig. 26, under surface. On the right side of the 

 mouth-angle are seen three, and on the left only two mouth-pai)illa\ Above these are the large 

 mouth-tentacles ; and still higher may be seen the points of the scales of the first pair of mouth- 

 tentacles. Fig. 27, upper surface. Fig. 28, arm-spines, from the side. 



Amphiura Barbarae, Figs. 32 - 34, -Y-. Fig. 32, under surface. The tentacles ai-e thick ; 

 their scales minute. Fig. 33, upper surface, with wide upper arm-plates. Fig. 34, arm-spines. 



Amphiura flexuosa 1 Ljn., Figs. 35 - 37. Fig. 35, Y; under sm-face, showing its very 

 minute, feeble scaling. Inside the mouth-shield are two small mouth-papilla;, followed by the 

 little jaws bearing the other pair of papillae ; beside these are seen the second pair of mouth- 

 tentacles, and the scales of the first pair. Fig. 36, Y'. "Pper surface, with the radial shields 

 separated by a central row of scales, and some others, ill-defined, on either side. Fig. 37, ^-, 

 third and fourth arm-spines, which differ from the rest in being stouter, a little rough, and in 

 having a microscopic beak at the tip. See also Plate V. Fig. 68. 



Amphiura repens, Figs. 38 - 40, -4&. Fig. 38, under sm-face. Most of the interbrachial 

 space is naked, as in A. semiermis. The'narrow jaw can-ies six bead-like mouth-papillaj. Fig. 

 39, ujiper sm-face, which much resembles that of the East Indian A. hwis. Fig. 40, arm-spines. 



Ophioceramis albida (Amphipholis Ljn.), Figs. 29-31, V-- F'g- 29, under surface. 

 The lai-ge side mouth-shields, numerous mouth-papillEe, and short genital openings are the char- 



