52 THE VOYAGE OF II. M.S. CHALLENGER. 



no trace of the presence of any pedicellarise whatever on the actinal surface, whilst in 

 Pontaster Jbrcipatus of this size, and even smaller, these organs form a most conspicuous 

 feature, being already well developed in the smallest example I have examined. No pedi- 

 cellaris? are to be found anywhere on Pontaster pristinus. 



Notwithstanding the incompleteness of the above summary of the characters of this 

 young starfish, they appear to me sufficient to show that we are dealing with a distinct 

 species. The great depth at which it occurs (2650 fathoms) is worthy of note. 



Colour in alcohol, a dirty ashy or slightly brownish grey. 



Locality. — Station 325. Off the coast of South America, east of Buenos Ayres. 

 March 2, 1876. Lat. 36° 44' 0" S., long. 46° 16' 0" W. Depth 2650 fathoms. Blue 

 mud. Bottom temperature 32° ■ 7 Fahr. ; surface temperature 70°'S Fahr. 



10. Pontaster venustus, n. sp. (PI. VIII. figs. 5 and 6 ; PL XII. figs. 5 and 6). 



Rays five. R = 37 mm. ; r = 8 mm. R > 4 '5 r. Breadth of a ray near the base, 

 8 '5 mm. 



Rays elongate, rather broad at the base, and thence tapering continuously up to a 

 finely pointed extremity. Interbrachial arcs well rounded. Abactinal surface of disk 

 and rays flat, slightly sloping from the centre of the disk to the extremity of the rays. 

 Actinal surface flat and level. 



The paxilke of the abactinal area are small and rather widely spaced, with a crown of 

 five to eight small papilliform spinelets in those situated about midway between the centre 

 and the extremity of the ray, and six to ten, or occasionally more, in those upon the disk. 

 The larger paxillse in the respective regions have frequently a single delicate, hairlike, 

 central spinelet, longer than the diameter of the whole crown of the paxilla, and four or 

 five times longer than the small papilliform spinelets that encircle it. No order of arrange- 

 ment is presented by the paxillse. No pedicellarise of any kind are to be found on the 

 abactinal area, or indeed anywhere upon this species. 



The marginal plates are conspicuous in the abactinal view, and form a well-defined and 

 slightly raised border to the disk and rays — the breadth, however, diminishing consider- 

 ably towards the extremity of the rays. The supero-marginal plates are twenty-five or 

 twenty-six in number from the median interradial line to the extremity. Their breadth 

 at a little distance from the base of the ray is about equal to their height, and their 

 length is rather greater than their breadth, often nearly one-third. Each supero-marginal 

 plate, excepting the first on each side of the median interradial line, bears a single 

 moderately-long conical pointed spine, standing on the middle of the rounded angle of 

 the plate, and directed laterally and very slightly forwards at an angle of about 45° to the 

 abactinal surface of the ray. These spines are robust at the base, and borne on a slight 

 prominence. They increase in length up to the fifth plate from the median interradial 

 line, where they measure 2*5 mm., and then decrease slowly and gradually up to the 



