106 Mr. W. K. Fisher'* Notes on Asteroldea. 



seems to be more nearly allied to Pedicellaster than to either 

 Heliaster or to any of the recently proposed genera of 

 Asteriidte. I would therefore place Labidiaster in the Pedi- 

 cellasteridse. I have dissected a large example of Labidi- 

 aster radiosus, Liitken, from the Straits of Magellan. 



Labidiaster differs from 'Brisinga, Odinia, Freyella, and 

 similar genera in the following important particulars : — 



(1) Its abactinal skeleton is not duplicated in the Brisingidae ; 



(2) forficifomi, 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 Brisingidse ; (4) the ambula- 

 cralia are shorter, especially the dorsal ends, which overlap, 

 or imbricate with, the next adoral ambulacra] plate, while in 

 the Brisingidse there is no sign of imbrication, the atnbula- 

 cralia resembling the centra of chordate vertebrae, with vertical 

 articulating adoral and aboral facets. 



In the Brisingidse (in the narrower sense) the abactinal 

 skeleton of the rays is variable, being in the form of trans- 

 verse, 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 lessspinit'erous, together with differentiated transverse 

 costae. 



In Labidiaster the skeleton of the ray is closely similar to 



volsellatus, briareas, and halicepus. Coronaster includes Hcterasterias, 

 Verrill, type Asterias volsellata, Sladen. In the above paper the following 

 remarks occur : — " The family affiliations of L'oronaster are not easy to 

 determine, its lineage being somewhat involved. The tendency to 

 crowding iu the arrangement of pedicels partakes of the Asteriidas, while 

 its mouth-plates are quite as ' brisingoid ' as those of Odinia, and perhaps 

 more so than the oral angles of Labidiaster, two groups placed in the 

 Brisingidag. Its skeleton is more like that of a simplified Pedicellaster 

 than like that of Asterias or allies. Parenthetically, the mouth-plates of 

 Pedicellaster are more prominently ' adambulacral ' than those of any 

 genus of the Asteriid*, even of Coscinastcrias, and are nearly or quite as 

 prominent, relatively, as the oral angles of Brisinga. In Pedicellaster 

 and Coronaster the ambulacral plates are more ' brisingoid/ uncrowded, 

 and the pedicel-pores are in two series, even if later the feet themselves 

 lie in four ranks. In very large specimens of Coroiiaster the pedicel- 

 pores form two slightly zigzag rows, much less pronounced than in small 

 specimens of Coscinasterias (in the broader sense), and the ambulacralia 

 are less crowded. My own feeling is that, until we arrive at a more 

 satisfastory basis for the subdivision of the Asteriidas than is now current, 

 it will be much better to leave Coronaster in the Pedicellasteridae." 



