2i6 DISCOVERY REPORTS 



Marginal plates lateral in position. Superomarginals with 3 spinelets, reduced to 2 

 and I at end of ray. Inferomarginals with 2 spinelets, reduced to i distally, before the 

 reduction of superomarginal spinelets occurs. Actinals with i spinelet. 



The skeleton is basically like that of ^. coscinactis (Fisher, 1928, pi. 29, fig. i) but the 

 skeletal intervals relative to size of plates are much smaller ; that is, the mesh is less open. 

 If the specimen were larger (R 63 mm. in coscinactis) it is possible the difference would 

 be less. The secondary ossicles uniting inferomarginals to actinals of coscinactis are 

 lacking in australis, while the secondary intermarginal ossicles extend only a fourth the 

 length of ray (in larger specimens, undoubtedly farther). The dorsolateral skeleton is 

 irregular as in coscinactis, the plates 3- and 4-lobed, and the smaller papular areas are in 

 about 3 irregular longiseries. There is one series of actinals extending far along ray and a 

 short second series about one-third length of ray. The papular areas are distributed as 

 in the figure of coscinactis but contain a single papula, except for a few intermarginal 

 areas proximally which have 2. 



In a smaller specimen (St. WS 86) most of the proximal dorsolaterals are 3-lobed and 

 imbricate more regularly. 



Adambulacral spines conspicuously longer than marginals and actinals, disposed in 

 transverse series, 4 on first 3 or 4 plates, then 3. The outermost spine is clavate, the 

 furrow spine terete and much more slender, while the middle one is intermediate. Each 

 mouth-plate has 2 short spinelets on the inner border, extending over the peristome; 

 and in line with the inner spinelet is a series of 3 successively longer ones on the surface 

 of the narrow plates. On the distal furrow corner of plate is a spinelet conspicuously 

 shorter and slenderer than outermost suboral. The first pair of adambulacrals behind 

 mouth-plates is separated by a slight interval. The disposition of oral spines is closely 

 similar to that of A. coscinactis (Fisher, 1928, pi. 29, fig. \b). 



Madreporic body small, with few coarse striae, situated near margin at top of inter- 

 brachial sulcus. 



There are no straight pedicellariae. The crossed closely resemble those of A. cosci- 

 nactis, diflrering only in minor details. They vary in length from o-i8 to 0-4 mm., the 

 greater number being 0-27-0-35 mm. in length. The largest are found on the actinal and 

 inferomarginal plates where they are mixed with average sized; while the smallest are 

 on the abactinal surface, there mixed with medium sized which are slightly smaller than 

 the actinal average. 



The gonads open in the interval between the inferomarginal and actinal plates, 3 or 

 4 mm. from the interbrachial angle. Each gonad consists of a cluster of relatively large 

 branched tufts, the lobules being irregular in form and unequal in length. The inter- 

 brachial septum is very rudimentary, practically non-existent, the coelom of disk being 

 therefore undivided. This is an advantage to the animal which ingests its food entire. In 

 the stomach of a specimen with disk diameter of 9 mm. were two gastropod shells, the 

 larger a sharp cone 9 mm. long. 



Type locality. St. WS 248, East Falkland Island, 52° 40' S, 58° 30' W, 210-242 m., 

 fine green sand, pebbles, shells, 3 specimens. 



