202 DISCOVERY REPORTS 



membrane, equals or slightly exceeds in length the longest marginal spine. Sometimes 

 a short accessory suboral is present on outer half of plate. 



The largest specimen having more than 5 rays (6-rayed) measures: R 56 mm., 

 r 38 mm. The 7-rayed example measures: R 35 mm., r 21 mm. The 8-rayed example 

 measures: R 40 mm., r 29 mm. In all respects other than number of rays these speci- 

 mens are typical verrucosus. The differences which Koehler believed sufficient to justify 

 a new species, norde7iskjdldi, are either not constant or else not characteristic. For 

 instance, the difference in the appearance of the abactinal surface (Koehler, 1923, p. 80) 

 is merely a difference such as may exist between two 5-rayed specimens, as well as 

 between a 5-rayed and 6-rayed. Sladen's figure of the abactinal surface of the type of 

 verrucosus indicates the areolated, or honey-combed, condition which is even more 

 accentuated in some of the 5- and 6-rayed examples before me. The supradorsal 

 membrane in such specimens is sunken within the circle of props formed by io± peri- 

 pheral paxillar spines; while the longer, heavier central spine of the paxilla forms a 

 characteristic eminence in the middle of each areole (Sladen, pi. 77, fig. 9). Sometimes, 

 due to a variety of causes (such as crowding in container), the supradorsal membrane 

 does not exhibit this areolated appearance. There appears to be no essential difference 

 between the 5-rayed and 6- to 8-rayed examples in the adambulacral and oral armature 

 nor in the size of the tube-feet. 



Fortunately, a z^-rayed specimen having R 50 mm. (St. WS 85, 25 March 1927) was 

 found to be carrying young in the supradorsal space. These occupied chiefly the lateral 

 portions of the interradii, but smaller young were found in one ray two-thirds the 

 distance to tip. The number of young in each interradius was as follows : A, i with 4 

 rays, 3 with 5 rays; B, 2 with 5 rays, 2 with 6 rays; C, 4 with 5 rays, 2 with 6 rays; 

 D, 2 with 5 rays, 2 with 6 rays, i with 5 mouth angles but 6 rays ; E, 5 with 5 rays, i 

 with 6 rays. Total: 25, of which 16 had 5 rays, 8 had 6 rays and i had 4 rays. It is 

 therefore obvious that the 6-rayed condition is much more fundamental than in multipes 

 where it is very rare. 



The largest of these 25 young has 5 rays and measures R 9 mm., r 6 mm. The first 

 adambulacral comb contains 4 spines; the next, 5, the innermost being very small; then 

 3 plates with 4 spines; then one with 5, innermost very small; then 3 plates with 4 

 spines, etc. The oral angle has a fan of 8 completely webbed spines. The crowding of the 

 tube-feet is already very apparent but the adambulacral plates have not yet become 

 differentiated into two sorts. The actinolateral membrane is about as broad as in the adult. 

 There are about 8 peripheral paxillar spinelets and i central. The osculum is as well 

 developed as in the adult. 



A 6-rayed young, with R 5 mm., found in the same interradius, has essentially the 

 same spine counts. 



The smallest of the 25 has 6 rays with R 3-5 mm. It was found together with a 5-rayed 

 young rather far along the ray. Adambulacral combs contain mostly 4 spinelets each. 



In a b-rayed specimen (St. WS 243, 17 July 1928), having R 38 mm., nine 6-rayed young 

 and one 5-rayed were found. Two 6-rayed young, with R 6-5 and 7-5 mm. were about 



