CLARK : AUSTRALIAN AND INDO-PACIFIC ECHINODERMS. 129 



few (3-6) and short. Teutacle-scale single and very large ; on basal pores of 

 arm supplementary scales of small size and irregular position are occasionally 

 present. No pores between under arm-plates. Genital slits two in each inter- 

 brachial area. 



Type-species, B. lacertosa (Pedinura) Lyman, 1883. Bull. M. C. Z., 10, p. 231, pi. 3, 

 figs. 4-6. 



This is a very natural group of large, deep-water ophiurans, all but one of 

 which have been referred hitherto to the genus Pectinura in spite of the rudimen- 

 tai-y condition of the supplementary oral plates. The Ophiopeza reducta of 

 Koehler (1907, Bull. Sci. France et Belgique, 41, p. 283) differs from the other 

 species not only in its elongated radial shields, but also in its coloration, for 

 while they are uuicolor (whitish in alcohol or dry), Koehler's single specimen of 

 0. reducta shows traces of a variegated disc and annulated arms. Koehler very 

 naturally considers that this coloration would indicate a shallow-water habitat, 

 and if such is the case, 0. reducta would differ markedly from the other species 

 of the genus in that particular. However, its structural peculiarities appear to 

 necessitate its being placed in this genus, at least until we have further light on 

 its distribution and variability. 



Key to the Species of Bathypectinura. 



Arm-spines 3 or 4. 



Radial sliields not twice as long as wide ; under arm-plates not quadri- 

 lateral, the first one wider than long. 

 Oral sliields wider than long ; arm-spines longer than \ arm-joint. 

 Disc including more than 4 basal arm-joints; upper arm-plates 

 highly arched so that arm-spines appear low down on side of 



arm lacertosa 



Disc including not more than 3 basal arm-joints ; upper arm- 

 plates not highly arched so that arm-spines do not appear low 



down on side of arm elata 



Oral shields longer than wide ; arm-spines shorter than \ arm-joint ; 



disc including more than 4 basal arm-joints heros 



Radial shields 3 times as long as wide ; under arm-plates quadrilateral, 



the first one longer than wide reducta 



Arm-spines 5 or 6. 



Lowest arm-spine longest, equal to arm-joint modesta 



Arm-spines subequal, about ^ as long as arm-joint. 



Interbrachial areas (orally) densely granulated conspicita 



Interbrachial areas with many bare plates, surrounded by granules (essellata 



Bathypectinura lacertosa. 

 Pectinura lacertosa Lyman, 1883. Bull. M. C. Z., 10, p. 231, pi. 3, figs. 4-6. 

 Off Grenada, 159 fms. 



VOL. LII. — NO. 7 9 



