170 Ml-. W. K, Fislier on AsterolJea. 



Asteroltlea, 1889, p. 102, as tlie first diagnosis in tlie " Narra- 

 tive of the 'Challenger' Expedition" (vol. i. p. 609) con- 

 tained no specific names. The first species, and only adult 

 form, is L. tartarens, and this may serve as type. The other 

 species, L.forcip'ifer, seems to be founded upon immature, or, 

 at least, very small specimens, and wliether the adult is like 

 tartareus or a species of Vips^caster is not known. L. tar- 

 tareus has a small spine on each marginal plate, rather small 

 actinal interradial areas, and seems to me to be near Dyfasier. 

 I have seen the type in the British Museum. 



Metrodira, Gvaj,andi(s Sysiematic Position. — This puzzling 

 genus was placed in the Linckiida3 by Sladen (' Challenger' 

 A>*teroidea, 1889, p. -115), and other writers have followed 

 him. 



Metrodira shows an outward resemblance to the Asteropidfe, 

 barring the single feature of the slender rays. De Loriol * 

 described a very young specimcTi as Scaphaster humberti, 

 which he placed in the Gymnasteriidie ( = Asteropidce) near 

 Asteropsis ( = Petrlcia, Gray). 



Sladen {loc. cit.) stated that " its external facies and 

 oeneral structure appear to indicate an intermediate position 

 between the Linckiidfe and Echinasteridse." 



Unfortunately the specimens at my disposal are small. 

 The characters which would lead one to place this genus in 

 the Asteropidte (restricted to Asierope and Fetrici'i) are as 

 follows : — The thin skin which covers the plates and spines ; 

 the conspicuous marginals, not unlike those of Petricia; the 

 loosely tessellate abactinal skeleton, bearing skin-covered 

 .spinelets. The characters which are adverse, so to speak, 

 are : — The conspicuous series of interniarginal plates, the 

 absence of actinal intermediate plates^ except a single plate 

 back of the mouth-jdates ; the rudimentary interbrachial 

 septum without a calcareous pillar (perhaps due to small size 

 of disk) ; the single ampulla to each tube-foot. 



The features which seem to ally Metrodira to the Echin- 

 asteridte are : — The single ampnllfe, spinose abactinal plates, 

 and the adambulacral armature. Tlie intermarginal plates 

 and the very reduced actinal intermediate areas are entirely 

 consistent with this family, but the very conspicuous mar- 

 ginal plates are not. The interbrachial septa are rudimentary, 

 practically absent, although it is not possible in the small 

 specimens at my disposal to be certain of this point. 



* yUm, soc. pli.y*. et d'hist. natur. Geneve, vol. xxxiii. pt. 2, uo, 1, 

 p. 27. ' 



