418 THE VOYAGE OF H.M.S. CHALLENGER. 
into the Abyssal zone. Zoroaster ackleyx and Zoroaster sigsbeet do not 
extend below the Continental zone, but the former is also found in the deep 
water of the Littoral zone. ; 
Greatest range of one species: Zoroaster diomedex, 38 to 1555 fathoms. 
y. Nature of the Sea-bottom: Zoroaster fulgens and Zoroaster tenwis on Blue mud, 
the former was also found on Red mud off Pernambuco (in 675 fathoms). 
Zoroaster diomedex on Globigerina ooze. Zoroaster ackleyi on coarse sand 
and broken shells. Zoroaster sigsbeez on fine sand. 
The species collected by the Challenger are indicated in the foregoing list by an 
asterisk. 
Chorological Synopsis of the Species herein mentioned. 
| 
Ocean. Range in Fathoms. Nature of the Sea-bottom. 
Zoroaster fulgens : : Atlantic. 500 to 1350. Blue mud; Red mud. 
Zoroaster tenuis . : é Pacific. 1070. Blue mud. 
1. Zoroaster fulgens, Wyville Thomson (Pl. LXVI. figs. 1 and 2; Pl. LXVIII. figs. 
1 and 2). 
Zoroaster fulgens, Wyville Thomson, The Depths of the Sea, 1873, p. 154, fig. 26. 
Rays five. R=125 to 130 mm.; r=14to15mm. R>85r. Breadth of a ray at 
the base, 17 mm. 
Rays very long, narrow, subcylindrical, and tapering throughout to a finely pointed 
extremity ; arched on the abactinal surface, and tumid on the actinal surface on each 
side of the furrow, which is deeply sunken. Interbrachial arcs acute. 
The disk is rather higher than the rays and slightly tumid. The calcareous skeleton of 
the whole test is formed of suboval or subhexagonal plates, disposed in perfectly regular 
longitudinal and transverse series. The following is the arrangement they present. 
Surrounding a dorso-central and five small radially placed under-basal plates, are five 
large basal plates interradial in position ; and outside and alternating with these are five 
similar but rather smaller radially placed plates, the primary radials. Outward from each 
of the radial plates proceeds a longitudinal series of plates which extends along the median 
abactinal line of the ray, each plate regularly subhexagonal in form, and touching or 
shghtly imbricating upon its next serial companion. On each side of this median line of 
plates is a parallel line of smaller plates, and these are succeeded by a series of plates 
nearly equal in size to those of the median line ; the outer of these lines standing on the 
convexity which separates the abactinal and lateral areas of the ray. Between this series 
