182 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



paxilla having 1 to 4 central and 8 to 10 peripheral spinelets, while 

 a proximal radial plate bears 8 or 9 central and about 15 peripheral 

 spinelets (in addition occasionally to an equally long tapering spini- 

 form pedicellaria). In fully grown examples of typicus from 

 Samoa corresponding lateral paxillae have G or 7 spinelets only 

 (usually all peripheral) and the median radial 7 or 8 (occasionally 

 1 central). The measurements of the specimen are: R = 32 mm., 

 r = 6 mm., R = 5.3 r; breadth of ra}^ at base, 7 mm. 



Type-locality. — "Java; Isle de France." 



Distribution. — Mauritius, Java, Philippine Islands, Port Darwin; 

 Torres Strait ; Freemantle, W. Australia ; New Guinea ; Fiji Islands 

 (Studer). 



Specimen examined. — Station 5165, off Observation Island, south- 

 west end of Tawi Tawi Island, Sulu Archipelago, 9 fathoms, coral; 

 1 specimen. 



Family BENTHOPECTINIDAE Verrill. 

 Genus PECTINASTER Perrier. 



Pectinaster Pebbieb, Ann. sci. nat., vol. 19, 1885, p. 70. Type, P. filhoU 

 Perrier. 



KEY TO THE SPECIES AND SDESTECIES OF PECTINASTEH HEREIN DESCRIBED. 



a\ Central spine of paxillae absent from a narrow area at either side of paxillar 

 area of ray ; 15 to 18 adambulacral plates correspond to first 10 inferomar- 

 ginals ; marginal spinelets fewer, a bare space on the central part of mar- 

 ginal plates. 



b\ Spinelets accompanying abactinal spines not greatly reduced in num- 

 ber on middle and distal portions of ray; marginal spines moder- 

 ately robust mimicus, p. 182. 



b^ Abactinal plates of ray with very few spinelets accompanying the 

 spine (1 to 4, distally, 0) ; marginal spines robust. 



palaioanensis, p. 185. 

 a\ Central spine of paxillae distributed abundantly all over abactinal area ; 13, 

 rarely 14, adambulacral plates to first 10 inferomarginals ; marginal spines 

 more numerous, no well-defined bare space on the plates. 



hylacanthus, p. 187, 



PECTINASTER MIMICUS (Sladen). 



Plate 49, fig. 1. 



Pontaster mimicus Sladen, 1889, p. 48, pi. 4, figs. 1 and 2; pi. 7, figs. 



5 and 6. 

 Pectinaster mimicus, Pereieb, 1894, p. 279. — Ludwig, 1910, p. 449. — Fisheb, 



1911rf, p. 126. 



Notes on specimens. — I have experienced great difficulty in apply- 

 ing a name to these specimens, there being three in the field which 

 might prove to be applicable: P. mimicus^ P. hispidus (Wood-Mason 

 and Alcock), and P. forcipatus., var. echinatus (Sladen). Wood- 

 Mason and Alcock do not state definitely wherein their species differs 

 from P. mimicus. According to Ludwig, 1910 (p. 450), mimicus 



