ECHINODEEMATA. 159 



syzygy. Ten arms. First brachials wider without than within, in 

 contact, with a convex median protuberance along their distal edge ; 

 the second with sides a little more regular ; the third almost square, 

 p. syzygy. The fourth to seventh joints a little wider than long ; 

 eighth or ninth a syzygy. The succeeding joints wedge-shaped, 

 with their free margins a little overlapping and slightly toothed. 

 About 5-8 joints between the succeeding syzygies. 



The earlier pinnules are extraordinarily stiff; the first, which is 

 on the second brachial, is much shorter than the second or third, 

 which are of about the same length and made up of rather less than 

 20 joints, most of which are longer than wide, and have their distal 

 edge enlarged and slightly denticulated. There are 10 or 12 stiff 

 pinnules ; the succeeding ones are shorter, and then again longer. 



Arms more than 120 miUim. long ; disk not more than 7 miUim. 

 in diameter. The radials and the earlier brachials have their 

 infero-lateral edge produced into a kind of ledge. The more 

 proximal joints have the appearance of being tuberculated, and 

 there is a faint median dorsal ridge ; at the sides they are com- 

 pressed. 



Colour dark slate. 



The stiff pinnules, the long arms, and the small disk are very 

 striking characters in this species. 



Port Denison. 



The large Myzostomum found on it has been named M. coriaceum 

 by Dr. Graff. 



8. Antedon decipiens. (Plate XI. figs. B, a.) 



CeBtrodoTsal small ; cirri on three levels, about 20 in number, 

 with 25 joints, of which the fourth to tenth are longer than wide ; 

 the rest, which gradually become shorter, are provided with a weU- 

 marked spine; these decrease towards the end, but the penultimate 

 one is larger again. 



First radials quite distinct; the second oblong, three times as 

 long as wide, partly in contact ; the third almost triangular. The 

 arms may or may not divide, so that there are from about 14 to 18. 

 The first brachials or first distiehals are always wide, and touch ; 

 where the arms divide there are three distiehals, and, the axillary 

 may be a syzygy. The first brachials, which have sharp overlapping 

 distal edges, are pretty regularly oblong ; at about the seventh they 

 become alternately wider on either side, to again become more 

 regular later on. 



Syzygies 3, 12-15, 22-25 ; then from ] 0-12 joints between each 

 syzygy. 



First pinnule on second distichal (when present), that and the 

 one on the third brachial short ; those on fifth to ninth much longer, 

 the basal joints very stout, the free ends very delicate, and their 

 outer side produced into a well-marked conical process. The suc- 

 ceeding pinnules are shorter, and these again increase in length ; 

 they are not composed of a large number of joints. 



