STARFISHES OF THE PHILIPPINE SEAS. 493 



are joined by one or two overlapping, oblong, intermediate ossicles. 

 There results an open, fairly regular, reticulate skeleton having 

 large tetragonal meshes (except where the dorsolateral 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 re- 

 mains 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 arma- 

 ture of the adambulacral plates are as in Corona-ster. The arrange- 

 ment of the pedicellariae either on retractile wreaths surrounding 

 the spines or on retractile transverse cushions is not unlike that found 

 in Coronaster. The mouth plates of the Brisingidae, of Gorona8ter, 

 Pedicellastei\ and of Lahidiaster are similar in general form, those 

 of Labidiaster being relatively the smallest. 



The features which are chiefly relied upon to distinguish the Bri- 

 singidae, and to which the family in part owes its characteristic ap- 

 pearance, are conspicuous by their different form in Lahidiaster. 

 Such, in the Brisingidae, are the elongate and peculiarly formed 

 adambulacral plates; the long needle-like subambulacral and mar- 

 ginal 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 RatKbunaster (type, RatKbunaster californicus, from off 

 California, deep water) was described by me as a neighbor of the 

 curious polybrachiate Pycnopodia of Stimpson. I think the genus 

 is related, instead, to Coronaster. It is notable for the suppression 

 of the alternate superomarginal plates and the reduction of the abac- 

 tinal skeleton to spaced circular plates without trace of connectives. 

 The marginal and abactinal plates bear an acicular spine surrounded 

 by a retractile sheath with an expanded distal crown covered with 

 numerous pedicellariae. The ambulacral, adambulacral, and oral 

 plates are similar to those of Coronaster. 



In Labidiaster^ Coronaster^ RatKbunaster, and certain genera of 

 the Brisingidae there are two gonads to each raj'' ; each gonad opens 

 upon the side of the ra}^ at some distance from the base. All three 

 genera, as well as the Brisingidae, have a single ampulla to each 

 tube foot. 



1 Verrill, in his " Monograpli of tlie Sliailow-water Starfislies of tlie North Pacific Coast," 

 1914, p. 352, proposes a new genus, Lahidastrclla, for Lahidiaster annulatuK, Sladcn. " Tt 

 differs considerably in structure from L. radioHus, especially in having the dorsal and 

 superomarginal 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. radinsus, and is carried further in /.-. anniilatus. I agree with 

 Koehler that it does not form a safe basis for a generic division between two otherwise 

 similar species (Koehler, Ann. de rinstitut oceanographique, vol. 7, fasc. 8, May 1917, 

 p. 8). 



