Mr. W. K. Fisher's Notes on Aster oidea. 107 



that of Goronaster. There is a longitudinal series of tri- 

 lobate infero-marginal plates, one of quadrilobate or cruci- 

 form supero-margiual plates, and one of cruciform median 

 radial plates. The marginals and radials form regular 

 transverse series. On the basal portion of the ray there is a 

 more or less irregular zigzag series of trilobate dorso-lateral 

 plates. The primary plates either connect directly by their 

 slender lobes, or these are joined by one or two overlapping, 

 oblong, intermediate ossicles. There results an open, fairly 

 regular, reticulate skeleton having large tetragonal meshes 

 (exeept where the dorso-lateral plates frame pentagonal 

 openings). On the outer part of the ray the longitudinal, 

 intermediate, connecting plates and the longitudinally oriented 

 lobes of the marginals and radials gradually disappear, so 

 that there remains only a series of independent, transverse, 

 slender skeletal bands, simulating those of Brisinga, but 

 having a very different history *. The skeletal meshes 

 contain numerous papulae. The form and armature of the 

 adambulacral plates are as in Goronaster. The arrangement 

 of the pedicellarise either in retractile wreaths surrounding 

 the spines or in retractile transverse cushions is not unlike 

 that found in Goronaster -\. The mouth-plates of the Bri- 

 singida?, of Goronaster, Pcdicellaster, and of Labidiaster are 

 similar in general form, those of Labidiaster being relatively 

 the smallest. 



The features which are chiefly relied upon to distinguish 

 the Brisingidse, and to which the family in part owes its 

 characteristic appearance, are conspicuous by their different 

 form in Labidiaster. Such, in the Brisingidse, are the 

 elongate and peculiarly formed adambulacral plates; the 

 Jong needle-like subambulacral and marginal spines, with 

 their characteristic sacculate sheaths ; the variable but always 

 non-reticulate abactinal skeleton of the rays ; the presence 

 of only crossed or forcipiform pedicellariae. 



The genus Rathbunaster (type Ratkbunader cahfornicus, 



* Yen-ill, in his ' Monograph of the Shallow-water Starfishes of the 

 North Pacific Coast,' 1914, p. 352, proposes a new genus, Labidastrella, 

 for Labidiaster annulutus, Sladen. "It differs considerably in structure 

 from L. radiosus, especially in having the dorsal and supermarginal 

 plates nearly abortive distally, on the rays, beyond the genital regions." 

 It is evident that this tendency to lose the dorsal skeleton of the distal 

 part of the ray manifests itself in L. radiosus, and is carried further in 

 L. annulutus. I agree with Koehler that it does not form a safe basis 

 for a generic division between two otherwise similar species (Koehler, 

 Ann. de l'institut oceauographique, vol. vii., fasc. 8, May 1917, p. 8). 



t See Sladen's figures oiAsterius (= Goronaster) volsellata, ' Challen- 

 ger ' Asteroidea, pi. cvii. 



