I90 DISCOVERY REPORTS 



(5-5 mm.) to the outer (6-5 mm.). The stouter inferomarginal (7 mm.) is spaced from the 

 outermost subambulacral about twice the distance between the 2 outer subambulacrals. 

 All these spines are encased in a rather voluminous sheath which extends as a sacculus 

 beyond the tip, making of the actinal armature a crowded confusion of long pulpy 

 papillae. 



The mouth-plates have a broad actinostomial border, and are deeply excavated on the 

 furrow margin to accommodate the first tube foot. On the actinostomial border are 

 three prominent spines ; the inner is long, flattened, heavy ; the next two are smaller, 

 and the outer of these stands on a prominent angle of the margin. Near it, on furrow 

 margin, is a fourth subequal spine, and then a fifth nearly as large as the apical spme. 

 A suboral stands just back of the apical spine but is not so robust. There is consider- 

 able variation in the size of all these spines. 



Tube-feet are large, and crowded roughly (as to tips) in 4 series. They remind one of 

 Diplopteraster . 



There is an extensive, complete, membranous interbrachial septum attached on all 

 sides except that adjacent to eversible stomach. This free inner edge is about even with 

 border of actinostome. The interradial extent of the septum is about 40 mm. ; the 

 dorsoventral, doubtless quite variable, is 15 mm. 



The voluminous gonads are attached at the junction of the interradial septum with the 

 abactinal wall, from the interradial angle, at ambitus, nearly to the inner free edge of 

 septum, or along about 30 mm. They open by several pores into an unspecialized 

 interradial sulcus. The outermost gonopore is fair sized and is at the ambitus. Two or 

 three others can be detected when the integument is stretched under clear alcohol. 



These two Falkland specimens diflFer from Sladen's type in having stouter rays and 

 longer abactinal spines, and may represent a definite forma. But there are such marked 

 differences between the two specimens that it is unwise to draw any conclusions until 

 more material is available, the more so since the range of variation of the type form 

 may be extensive. Sladen described and figured a unique specimen. 



The specimen from off Marion Island measures R 64 mm., r 22 mm. (actual, not to 

 end of spines), br 30 mm. (to end of spines). There are i or 2 furrow spines and usually 

 4 subambulacrals. It appears to be typical folliculotiis. 



I add here a diagnosis of Peribolaster emended slightly from that which I published in 

 1911 (p. 341). 



Korethrasteridae having the abactinal surface paved with cruciform plates whose 

 delicate lobes are connected by supplementary ossicles, forming a fairly regular network 

 of large quadrangular meshes over the entire surface. On the centre of each primary 

 abactinal plate is borne, on a small boss, a fascicle of delicate subequal spinelets en- 

 veloped in membranous sheaths united in the interior of the fascicle. One to numerous 

 papulae in each mesh ; no actinal papulae. No actinal intermediate plates, the adambula- 

 cral plates imbricating with and sometimes fusing with the inferomarginals. Supero- 

 marginal plates cruciform and bearing a fascicle of spinelets ; inferomarginals with a 

 single prominent acicular spine, which forms with the similar adambulacral spines a 



