ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER. 121 



6'. Abactinal plates of i)apnlar areas low lab\ilate and strongly stellate, the larger bearing a central 



conspicuous spiiio surrounded by a circle ot more or less elongate spinelets; superomarginals 



with two or three and inferomarginals with two to five long bristling spines; odd interradial 



marginal plate not much if any more prominent than adjacent s\iperomarginals. 



c'. Papulae extending one-third to three-fifths length of ray; dorsal muscle bands weak; mouth 



plates with more than nine marginal spines each; odd interradial marginal usually absent in 



some of the iuterradii Nearchasler Fisher, p. 132. 



c*. Papulae extending one-seventh length ot ray; dorsal muscle bands strong, prominent; mouth 

 plates with less than eight marginal spines; odd interradial present in all interradii. 



Myonotus Fisher, p. 140. 

 6'. Abactinal plates flat or somewhat convex and, though frequently lobed, not strongly so, bearing 

 a central spine only, or several spinelets in addition, or one to several small spinelets; superomar- 

 ginals usually with only one large spine and inferomarginals with one or two primary spines; odd 

 interradial marginal prominent and usually present in all interradii. .Benthopeclen Verrill, p. 142. 



Rfmarlcs. — Members of tliis family have a very characteristic outward "habit" 

 and are easily identified with their group. This is dtie to the structure of the mar- 

 ginal and adambulacral plates, with their bristling armature, to the limited distribu- 

 tion of papulae, and to a less extent to the simple abactinal i)lates wliich commonly 

 have a slender central spine and a variable number of additional spinelets. They are 

 often in the form of simple paxill», but all gradations between paxillaj and flat 

 immersed plates occur. Another feature which lends a highly characteristic appear- 

 ance to members of this famih' is the form of the pedicellariae. When these occur 

 they are of the double pectinate variety, or a modification of this tj^je. That 

 is, a comb of modified spinelets is placed opposite another similar comb, each 

 occupying separate but closely juxtaposed plates, or tlie spinelets may be grouped 

 (fasciculated) on one plate or two neighboring plates. The double pectinate 

 pedicellariaj are strictly characteristic of tiiis family. 



Previous to Sladen's Challenger report (1889) the members of tiiis family were 

 not set apart by even subfamily distinctions from other Archasteridse; in fact some 

 species of Cheiraster and the tyj)e of Acantliardiaster were first described as ^' Ar chas- 

 ter." Sladen erected the subfamily Pararcliasterinje for the reception of Parar- 

 chaster and Ponlaster. In 1894 A'errill split this subfamily, recognizing the Bentho- 

 pectininfe for Benthopecten, and Ponta-steriniB for Poiitaster, Cheiraster, PeciinaMer, 

 and AcantJiarchaster. In 1899 the Benthopectinina) was rai.sed to family rank by 

 Verrill, and the Pontasterinse was placed in Ids new family PlutonasteridiB, near 

 Plutonaster and allietl genera. Believing that Sladen's grouping of genera more 

 nearly expressed the relationship, I placed the Pontasterinas under the Bentliopec- 

 tinidse in 1906. For reasons stated below the Pontasterinse has been abandoneil in 

 this report. 



The order Notom^'ota Lud\vig (1910) is coextensive with mj' Bentho]>ectinidfB 

 and is founded primarily on the characteristic dorsal muscle bands of the rays. 

 Ludwig recognizes two families, the Cheirasterid;« (Pontasterinaj Verrill) and 

 Benthopectinidir, the latter including only Benthopecten and Pararchaster restricted, 

 hence ha^^ng the limits originally set by Verrill. These two famihes are character- 

 ized by the absence or presence of unpaired interradial marginal plates, and by no 

 other features of importance. In the new genus Nearchaster, one or more, occasion- 

 ally all, the interradii have the odd marginal (not always in both series of the same 



