DISCOVERY REPORTS 



Primary ambulacral tubercles distinctly smaller than the interambulacral primaries ; 

 they are confluent till well above the ambitus. In the largest specimens the secondaries 

 along the median line are slightly enlarged so as to indicate median series. Primary 

 interambulacral tubercles confluent up to the ambitus. In the largest specimens the 

 secondaries are somewhat enlarged at the ambitus, forming fairly conspicuous secondary 

 series, sometimes also outside the primary series, but these outer tubercles are somewhat 

 smaller than those inside the primary series. Rarely there may be two enlarged secon- 

 dary tubercles inside the primary one, these three then forming together an oblique, 

 upward-turning series on each plate at the ambitus (Plate II, fig. lo). There is no naked 

 median space in either ambulacra or interambulacra. 



The apical system is fairly large, ca. 30 per cent of the horizontal diameter of the 

 disk. Oc. I is insert, as usual in Notechinus, but often Oc. II and V, or even also Oc. IV, 

 are insert. There is a rather broad naked outer margin on the apical plates. The periproct 

 is rather large, the plates very characteristically thin and flat, and perfectly smooth. The 



Fig. I. Apical system of Notechinus marlonis, n.sp., xq. 



suranal plate is, except in the small specimens, from a size of ca. 14 mm. h.d., usually 

 separated from the edge of the periproct by a series of small plates (Fig. i a, b). It 

 usually shows some concentric striations. The small plates round the anal opening are 

 raised into small papillae. The peristome, as typical of the genus, is wholly devoid of 

 plates outside or inside the buccal plates ; some few, very slender bihamate spicules are 

 found in the distal part. 



Spines rather slender, not exceeding a length oica. 10 mm., even in the largest speci- 

 mens ; those around the peristome slightly curved. Secondary spines slender, but, as 

 typical of the genus, not pointed. Pedicellariae as typical of the genus. The large globi- 

 ferous pedicellariae may have up to three teeth along either side of the blade ; but equally 

 often there are only one or two. The small globiferous pedicellariae with one tooth on 

 either side (Plate IX, figs. 2, 3). Both sorts of globiferous pedicellariae on the whole 

 rather numerous. Tridentate pedicellariae exceedingly scarce, often totally lacking. They 



