2i8 DISCOVERY REPORTS 



The subfamily as here understood is rather isolated and contains Coronaster Perrier, 

 Rathbimaster Fisher (eastern north Pacific) and Lobidiaster Liitken. 



Remarks. Verrill included only Labidiaster and the synonymous Labidiostrella in 

 this subfamily, which he placed in the Brisingidae, following the usual treatment of 

 Labidiaster. 



Labidiaster differs from Brisinga, Odinia, Freyella, and similar Brisingids in the 

 following important particulars: (i) its abactinal skeleton is not duplicated in the 

 Brisingidae; (2) forficiform, or straight, pedicellariae are present; (3) the adambulacral 

 plates are crowded, very short in proportion to width, and entirely unlike in form and 

 armature the same highly peculiar plates of all Brisingidae ; (4) the adambulacralia are 

 shorter, especially the dorsal ends, which overlap, or imbricate with, the next adoral 

 ambulacral plate, while in the Brisingidae there is no sign of imbrication, the ambula- 

 cralia resembling the centra of chordate vertebrae, with vertical articulating adoral and 

 aboral facets. 



In the Brisingidae (less Labidiaster) the abactinal skeleton of the rays is variable, 

 being in the form of transverse, independent, parallel ridges or costae, separated by 

 areas of integument without plates ; or the intervals may be partially or completely filled 

 in with more or less imperfectly developed plates immersed in the body wall ; or the 

 arches may be absent and a tessellation of thin plates may cover the genital region of the 

 ray; or there may be thin plates, more or less spiniferous, together with diflFerentiated 

 transverse costae. 



In Labidiaster the skeleton of the ray is closely similar to that of Coronaster. There is a 

 longitudinal series of trilobate inferomarginal plates, one of quadrilobate or cruciform 

 superomarginal 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 dorsolateral plates. The primary plates either 

 connect directly by their slender lobes, or these are joined by i or 2 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 ray the longitudinally oriented, intermediate, con- 

 nectives and similarly oriented lobes of marginals and radials gradually disappear on the 

 outer part of ray, so that there remains only a series of independent, transverse, slender, 

 skeletal bands. Even the abactinal elements of these are absorbed in Labidiaster annu- 

 latus. The skeletal meshes contain numerous papulae. The form and armature of the 

 adambulacral plates are as in Coronaster. The arrangement of the pedicellariae either in 

 retractile wreaths surrounding the spines or on retractile transverse cushions is not 

 unlike that found in Coronaster. The mouth-plates of the Brisingidae, of Coronaster, 

 Pedicellaster, 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 Brisingidae, and to 

 which the family in part owes its characteristic appearance, are conspicuous by their 

 different form in Labidiaster. Such, in the Brisingidae, are the elongate and peculiarly 



