44 ON THE ECHINODERMATA OF THE 



A Starfish of rather depressed form, having five broad flat arras ; the proportion 

 of the greater to the lesser radius being about 3 : 1 approximately. The calcareous 

 skeleton of the abactinal surface forms a very regular network, and the large con- 

 spicuous paxillae that spring from the intersections form longitudinal series which run 

 parallel to the median line of the ray ; consequently only two or three of the middle 

 rows reach to the tip, although from fourteen to sixteen may be counted at the base of 

 the arm. The paxillae, which are very compact, have a remarkably large stout pedicle 

 nearly twice as wide as high, and bear a crown of spinelets, numbering from fifteen 

 to twenty, or even more in large specimens, in length about equal to the diameter 

 of the base. The spinelets are flat in young examples, and from the angles of 

 their apex, which is as broad or broader than the base, proceed two small denticles, 

 giving to the spinelet the appearance of a two-pronged fork; with increasing age, 

 however, the spinelets become multilaminate, and the number of apical denticles 

 corresponds with that of the laminae, which radiate from the median axis of the 

 spinelet. 



The papulae are in groups of from four to ten or twelve in number, varying according 

 to age and size. They are most numerous upon the disk, the interspaces between the 

 ossicles of the calcareous network being smaller further out upon the rays, where the 

 papulae are consequently fewer and the paxillee closer together. 



The sides of the rays are deep and perpendicular, and are bounded by a dorsal and 

 a ventral series of marginal paxillae ; they stand wide apart from one another, and are 

 about twenty (17-22) in number from the arm-angle to the extremity of the ray. The 

 paxillae of the dorso-lateral series are larger than the general paxillae of the dorsal area, 

 and are directed somewhat upwards. The ventro-lateral series, which are much larger 

 and very prominent, alternate with these, standing opposite to the interspaces, and are 

 directed at an angle downwards ; their pedicles are nearly twice as broad as the fore- 

 going and oval in section, whilst the spinelets attached to them are somewhat shorter 

 than those on the dorsal paxillae. There are no paxillae in the space between the 

 dorsal and ventral series above named, the sides of the rays being bare. 



Each adambulacral plate bears two series of spinelets: one which runs parallel to the 

 furrow, and is composed of three to five equal-sized spinelets ; and a transverse series of 

 three or four placed obliquely or even at right angles to the furrow-series, a thick 

 membrane uniting the spinelets and forming a webbed comb. 



The ventral interbrachial areas are large, and bear a number of paxillae arranged 

 in rows parallel with the furrow, two, three, or sometimes even more of such rows 

 being present. In the largest example we have examined the innermost row has 

 eleven or twelve paxilte extending from the median interbrachial line out along the 

 ray ; the next outermost numbers 5, the third 3, the angle thus left being filled up by 

 a solitary paxilla. The paxillaj are large and all covered with a thick membrane ; their 

 bases or pedicles are very short, and carry six to eight spinelets arranged somewhat like 

 a double fan, all radiating and directed outwards. The main group of paxillae which 

 stand upon the area are nearly equal in size, but the five or six most aboral ones of the 

 innermost row diminish in size as they recede from the mouth ; they do not extend 



