418 



THE VOYAGE OF H.M.S. CHALLENGER. 



into the Abyssal zone. Zoroaster ackleyi and Zoroaster sigsbeei 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 diomedese, 38 to 1555 fathoms. 



y. Nature of the Sea-bottom: Zoroaster fulgens and Zoroaster tenuis on Blue mud, 

 the former was also found on Eed mud off Pernambuco (in 675 fathoms). 

 Zoroaster diomedese on Globigerina ooze. Zoroaster ackleyi on coarse sand 

 and broken shells. Zoroaster sigsbeei 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. 



1. Zoroaster fulgens, Wyville Thomson (PI. LXVI. figs. 1 and 2 ; PI. 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= 14 to 15 mm. R> 8 - 5 r. 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 abactiual 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 

 abactiual line of the ray, each plate regularly subhexagonal in form, and touching or 

 slightly imbricating upon its next serial companion. On each side of this median line of 

 plates is a parallel Hue 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 



