REPORT ON THE ASTEROIDEA. 249 



ones and the margin are precisely similar to those above described, excepting that they 

 bear no large spine, their tabulum being occupied by nine or more small, equal, papilliform 

 spinelets, -which are well-spaced and radiate slightly apart as if the surface of the tabulum 

 were slightly convex. The paxillse of the outermost two rows are rather smaller than those 

 of the next two rows ; and those of the outermost series which represent the aborted 

 supero-marginal plates are the smallest. The paxillse of the median radial area are rather 

 smaller than those of the longitudinal series ; they are rotund, bear no central spine, but have 

 six to eight papilliform spinelets on the tabulum precisely similar to those above described. 



The infero-marginal plates bear along their median line a series of four to six uniform 

 spines, placed one behind the other : the inner two are very small and delicate, scarcely 

 worthy of being counted with the series ; but the outer four are robust, tapering, and 

 pointed, and increase in size slightly as they approach the margin, although the marginal 

 or lateral spine is sometimes slightly smaller than its predecessor, the longest measuring 

 about 4 mm. in length. The distance between the second and third spine from the 

 margin is often rather greater than that between any of the others, and the space is 

 occupied by two or three short, delicate, hair-like spinelets ; one or two are also usually 

 present between the other large spines. The margin of the keel is fringed on each side 

 with rather large ciliary spinelets. 



The adambulacral plates are broad but very short, as seen on the actinal surface, and 

 are united by wide ligamentous bands. Their armature, which has the appearance of 

 being borne on a narrow keel, consists of three spines, arranged one behind the other, in 

 transverse series in relation to the axis of the ray. The innermost or furrow spine is the 

 shortest, compressed laterally, slightly curved, slightly tapering, but more or less obtuse at 

 the tip. The second spine is fully two-thirds longer, more robust, only very slightly com- 

 pressed, very faintly bent near the base (indeed scarcely perceptibly), tapering, and rather 

 obtusely pointed. The third spine is similar, but straight, and is usually rather more 

 tapering and sometimes a shade shorter and more delicate than the second spine. External 

 to this spine and close to its base is usually a three-jawed pedicellaria, wide at the base 

 but with delicately tapering and pointed jaws, rather more than one-third the length of 

 the spine. One or two delicate ciliary spinelets may also be present. Occasionally a 

 second and similar pedicellaria stands between this and the spinelets of the infero-marginal 

 plates, which is either borne on a small intermediate plate (present between the adam- 

 bulacral and infero-marginal plates) or at the innermost extremity of the infero-marginal 

 plate ; or its position may be occupied by a small group of ciliary spinelets. 



The mouth-plates are elongate and narrow, with a series of large actinal or superficial 

 spines running parallel to the margin; which are normally much larger than the marginal 

 series, and increase in size as they approach the mouth. The spines at the innermost 

 extremity of the plates (two or four in number) are very long, and extend nearly to the 

 centre of the actinostome. 



ZOOL. CHALL. EST. — PART LI. 1888.) 32 



