REPORT ON THE ASTEROIDEA. 647 



of the mature ray of Freyella heroina, are taken into consideration, together with the 

 differences in the adambulacral armature and the simulation of the abactinal plates, I 

 consider it safer on the strength of the material at my disposal to rank the form under 

 notice as a distinct species. 



Genus Colpaster, n. gen. 



Kays elongate and subcylindrical as viewed from above, having the general character 

 of the rays of Brisingidse. Disk small and sharply defined, the rays being readily 

 detachable. 



Abactinal area of the disk and of the basal portion of the rays covered with small, 

 scale-like, imbricating, calcareous plates, which form a compact casement. The plates bear 

 minute isolated spinelets, those upon the disk being slightly larger than on the base of the 

 rays, and with their extremity denticulate. No papulse are present. 



Adambulacral plates only slightly longer than broad, widely spaced, the interspaces 

 being filled with ligament. Adambulacral armature consisting of two small equal inner 

 spinelets, one at each extremity of the furrow-margin, and two unequal spines on the 

 actinal surface of the plate, one large and robust. These are invested with membranous 

 sheaths covered with crowded pedicellarise. Eobust lateral spines are articulated on small 

 rudimentary infero- marginal plates intimately united to the adambulacral plates. 



An azygos interradial plate, shield-shaped and conspicuous superficially, separates the 

 first pair of free adambulacral plates, resembling the mouth-shield of an Ophiuran. 



Mouth-plates small, with an armature consisting of three mouth-spines proper, and 

 three large secondary or superficial mouth-spines on the actinal surface of each plate. 



Madreporiform body small, subtubercular, prominent, situated near the margin of the 

 disk ; striations few in number and simple. Anal aperture distinct, situated excentrally. 



Remarks. — Colpaster resembles Freyella in general habit and in the plating of the 

 disk and ovarial regions of the rays. It is distinguished, however, from that and from all 

 other forms by the presence of the azygos interradial plate external to the mouth-plates, 

 and by the character of the armature of the adambulacral plates and mouth-plates. 



Cliorology of the Genus Colpaster. 



a. Geographical distribution : — 



Atlantic : One species between the parallels of 20° and 30° N. 



Colpaster scutigerula, from south-west of the Canary Islands. 

 /3. Bathymetrical range : 1525 fathoms. 

 y. Nature of the Sea-bottom : Hard ground. 



