WEST IXDIAX STARFISHES 



139 



Young specimens, up to 25°^°" in diameter, are often generically 

 undeterminable, if pedicellarige are not present. At this stage 

 of growth there is usually only one papular pore developed, but 

 that is median at the base of the ray. A little later two more 

 appear, one each side of the first. These and later conditions 

 may coexist on the different rays of the same specimen, owing to 

 unequal rates of development. 



This genus is common in moderately deep water of all the 

 oceans. Some of the species descend to great depths. 



Pectin ASTER vixcenti (Per.) Ludwig. 



Cheiraster vincenti Perrier, Exped. Trav. et Talisman, pp. 270, 275, 1894 



(short description.) 

 Archaster mirahilis (pars) Perrier, Etoiles de Mer, p. 256, 1884 (= No. 



231, p. 258.) 



Luidiaster vincenti Ludvrig. Notomyota, op. cit. 1910, pp. 452, 453, 1910. 



According to the brief description given by Perrier in 1884 

 (p. 258) this species has the following characters, based on the 

 types from station 231 : 



The rays are rather short ; radii are 10°^™ and 50°^™ ; ratio, 

 1 :5. Super omarginal spines are 28. There are no large spines 

 on the central part of the disk. The adambulacral spines have, 

 on the actinal side, a group of three or four spines, instead of 

 one or two as usual. 



The superomarginal and inferomarginal spines are shorter 

 than in C. mirahilis. 



The dorsal parapaxillae have mostly a larger spinule in the 

 center. 



The pectinate pedicellariae, on the interactinal plates, are well 

 developed, but variable in number and position, even on the dif- 

 ferent areas of the same specimen. There may be from one to 

 four, or none at all on any one area. 



In 1894 (p. 275) a few additions are made to the description: 

 The large inferomarginal spine is accompanied by two or three 

 smaller spines irregularly placed, and not constant. 



The papulas are arranged in a small median group, not very 

 prominent (as it is in Pontaster, sp.). He compares it to Pec- 

 tinaster oxyacanthus (Sladen, as Pontaster) but finds it quite 

 distinct. As Perrier states dictinctly that the papularium is 

 central "sur une plage impaire," this species should be placed in 

 Pectinaster, not in Luidiaster, where Ludwig located it, or else 



