i84 DISCOVERY REPORTS 



Genus Cuenotaster M. P. Thiery 



Leucaster Koehler (not Gauthier, 1887), 1912, p. 54. Type L. involutus Koehler. 

 Cuenotaster Thiery, ex Koehler, 1920, p. 159. 



Koehler by inadvertence compared Leucaster to Crenaster Perrier, a name without 

 status but regarded as synonymous with Dytaster. He intended to write Ctenaster 

 Perrier, 1884, which is also without status since it is preoccupied by Ctenaster Agassiz, 

 1835. Ctenaster Perrier, renamed Laetmaster by Fisher {Smithsonian Miscell. Coll., 

 Lii, 1908, p. 88), contains only one species, L. spectabilis, dredged in the West Indies in 

 1920 fathoms. 



Although in Laetmaster the abactinal plates are very numerous and independent as in 

 adult Cuenotaster, the adambulacral armature consists of a furrow comb of about 5 

 spinelets, and a subambulacral comb at a right angle to furrow, after the common 

 Solasterid pattern. The inferomarginal plates, less prominent and less widely spaced 

 than in Cuenotaster, show no trace of the latter's characteristic actinal double transverse 

 ridges, or keels, associated with the marginals. As in Cuenotaster the superomarginal 

 paxillae are not differentiated. So far as I am aware the only known specimen of 

 Laetmaster is the type which I have examined at the Museum of Comparative Zoology, 

 Cambridge, Massachusetts. 



Cuenotaster involutus (Koehler) 



Leucaster involutus Koehler, 1912, p. 55, pi. 5, figs, i, 2, 3, 6, 7, 10, 11. 



Cuenotaster involutus Koehler, 1920, p. 159, pi. 33, fig. 5; pi. 65, fig. 4. — 1923, p. 75. — Doderlein, 

 1928, p. 295. 



St. 42. Off mouth of Cumberland Bay, South Georgia, 120-204 m., 4 specimens. 



St. 45. Off Jason Light, South Georgia, 238-270 m., grey mud, i specimen. 



St. 140. Stromness Harbour to Larsen Point, South Georgia, 122-136 m., green mud, stones, 

 2 specimens. 



St. 148. Off Cape Saunders, South Georgia, 132-148 m., grey mud, stones, 2 specimens. 



St. 167. Off Signy Island, South Orkneys, 244-344 m., green mud, 2 specimens. 



St. 195. Admiralty Bay, King George Island, South Shetlands, 391 m., 7 specimens. This is the 

 type locality. 



St. 1952. Between Penguin Island and Lion's Rump, King George Island, South Shetlands, 

 367-383 m., I specimen. 



St. MS 71. East Cumberland Bay, South Georgia, 120-60 m., i specimen. 



Koehler has described and figured the external features of this species which is readily 

 recognized by the single series of prominent, bristling, spaced, marginal paxillae from 

 the base of which a double ridge passes to the adambulacral plates. The adambulacral 

 armature consists of a transverse series of 4 or 5 bristling tapered spines — the furrow 

 spine and the subambulacrals co-ordinated in a single series. In young examples the 

 abactinal skeleton is a very irregular, open mesh, enclosing small isolated irregular 

 plates. With advancing age (R 70 mm.) the plates of the mesh become entirely dissoci- 

 ated and immersed in the thick integument, which also increases in thickness with age. 

 These plates are very unequal in size, irregular, longer than wide, with tapered ends. 



