ECHINODEltMATA. 129 



longer in the median line of each ray, where they form a remarkably 

 regular series, continued on to the disk, but they become moro or 

 less ill-defined on the raised portion ; the granules on the rest of 

 the plates present no peculiarities, saving that thoy are a little 

 longer on the sides of the raised portion of the disk. The respira- 

 tory pores on this surface are rather large, scattered, and simple. 

 The supero-marginal plates are as much as 7 millim. high in the 

 widely opeu angle of the arms ; they are narrow, wider above than 

 below; as these plates pass outwards they decrease in length and 

 increase in breadth ; they next decrease in size generally, and 

 finally they are again, though much smaller, of the same general 

 form as those of the angles of the arm ; the terminal three or four 

 touch in the middle line: of these plates there are about 23 on 

 the side of each ray ; the condition of their armature is, perhaps, 

 best described by saying that some of the granules elongate to form 

 small spinous tubercles. The madreporic plate is situated about 

 one third of the radius from the centre of the disk ; it is prominent, 

 5-5 millim. long, and has the form of an irregular elongated oval. 

 The infero-marginal plates are likewise about 23 in number, and 

 their form in different regions presents very much the same varia- 

 tions as those of the supero-marginal series ; the granules, however, 

 do not present the same tendency to become spinous, though they 

 are all rather longer and not quite so closely packed. The adaru- 

 bulacral spines form a fringe of four flattened subequal spines, in 

 addition to which two smaller outer ones may be attached to the 

 same ossicle ; beyond these there are two or three much stouter 

 spines, and beyond these again there may be two or three spines, 

 the tips of which may be pointed. The granulation of the inter- 

 mediate plates presents very much the same characters as that of 

 the infero-marginal plates. 



This species may be distinguished from P. singularis or P. miliaris 

 by the length of its arms, and the shape and closer packing of the 

 plates of the abactinal surface ; from the former it is also distinguished 

 by having the adambulacral spines shorter and blunter, though they 

 are by no means as blunt as in P. miliaris, where the adambulacral 

 groove is so wide. 



Colour : the specimen whose admeasurements have been given in 

 the above description is dark slate; another, in which R = 82 and 

 r = 26, is light stone-coloured ; in it the disk is not elevated. 



Port Curtis, 5-11 fms. ; Prince of Wales Channel, 3-5 fms. 



18. Pentagonaster validus. 



This is a second new species which belongs to the Astrogonium 

 division of the genus. The arms are distinct, rounded, and stout, 

 the anus central and sometimes very distinct ; the granulation of 

 the ossicles is rather coarse, and only a few larger granules are 

 found scattered over the abactinal surface ; there are three rows of 

 adambulacral spines. 



As five specimens of this form were collected we are able to 



