2s6 DISCOVERY REPORTS 



meridionalis. In 2 series chosen at random the spines counts run as follows from base to 

 tip of ray:^ 5 m, id, im, id, 4m, id, 2m, id, im, 3d, im, id, im, id, i m, id, 

 2m: total 28 plates. Another runs: 7m, id, im, id, 2m, 2d, 4m, 2d, im, 2d, 3m: 

 total 26 plates. 



In these small specimens the skeleton is arranged as follows: a circle of plates (its 

 radius equal to Ir) on disk bearing i or 2 spinelets each, enclosing numerous isolated 

 monacanthid plates ; a carinal and 2 superomarginal series of monacanthid plates with a 

 zone of bare skin between, the superomarginals defining the abactinal area; a series of 

 monacanthid inferoniarginals and mixed monacanthid and diplacanthid adambulacrals ; 

 a few crossed pedicellariae attached to all plates except adambulacrals ; a broadly lanceo- 

 late straight pedicellaria on each mouth-plate, which carries i apical and i suboral spine. 



Studer's type oi Pedicellaster octoradiatus from South Georgia in which R is 6 mm. is 

 described as having an irregular calcareous net on the central part of disk, forming on the 

 rays three distinct bands, tube-feet biserial. This would apply to the three smallest 

 specimens listed above. 



Koehler did not describe the skeleton, but placed the species in Lysasterias {Anasterias 

 to him) by reason of the development of the circumspinal collars or pustules. After the 

 type reached the U.S. National Museum I made a dissection and described the skeleton 

 as follows (1922, p. 595): "It has a complete irregularly reticulate abactinal skeleton, 

 consisting of very numerous small, but fairly robust, oval, elliptical oblong, and a few 

 irregularly 3-lobed plates (which latter perhaps represent the primary dorsolaterals). 

 There is an irregular carinal series, of which the plates are no larger than the others. The 

 abactinal plates are joined to the superomarginals by transverse bands of plates which are 

 a little more regular than the others, and between consecutive trabeculae are broad (but 

 short) papular areas which form a zone just above the superomarginal plates. These 

 papular areas, or skeletal meshes, are larger than the other abactinal and the intermarginal 

 meshes. The marginal plates are fairly robust and of the form usually found in the 

 Asteriinae — namely, 4-lobed. The descending lobe of the superomarginal is the longest 

 and strongly overlaps the ascending one of the inferomarginal. The superomarginals are 

 regularly monacanthid, while most of the inferomarginals are diplacanthid. There is a 

 very inconspicuous series of small spineless actinal plates." 



This skeleton is like that of Diplasterias meridionalis, even to the obscured actinal 

 plates. I prepared the skeleton of one ray of meridionalis from St. MS 10, for comparison 

 with that of octoradiata from the same haul. These are more closely similar than is the 

 skeleton of the two formae of octoradiata ! In meridionalis and the typical form of octo- 

 radiata the actinals extend far along the ray whereas in forma eunota they stop at about 

 the middle of ray. PI. XXI, figs. 2-4. 



A comparison of alcoholic specimens reveals a striking similarity between the two 

 species except for the number of rays and number of adambulacral spines. Meridionalis 

 has the same broad "pustulate" collars around the spines, not less swollen or fleshy 

 than in octoradiata. 



' This means 5 monacanthid plates, i diplacanthid, i monacanthid, etc. 



