96 DISCOVERY REPORTS 



entrance to the Straits of Magellan, opposite Port Churruca, 245 fathoms, blue mud; 

 bottom temperature 46^ F. 



Distribution. Slopes of Falkland-Cape Horn Plateau, 350-500 m. 



Genus Luidiaster Studer 



Luidiaster Studer, Sitzungsber. naturforsch. Freunde, Berlin, 16 Oct. 1883, p. 131. Type L. hirsutus 



Studer. — Ludwig, 1910, p. 451. — Fisher, 1911, p. 127. — Verrill, 1914, p. 311. 

 Acantharchaster Verrill, Proc. U.S. Nat. Mus., xvn, 1894, p. 268. Type Archaster dawsoni Verrill. 



Luidiaster gerlachei (Ludwig) 



Cheiraster gerlachei Ludwig, 1903, p. 9, pi. i, figs. 1-8; pi. 2, figs. 9, 10. 



Luidiaster gerlachei Ludwig, 1910, pp. 252, 253. — Fisher, 191 1, p. 127. — Koehler, 1920, p. 244, pi. 55, 

 figs. 2-5; pi. 65, fig. 8. 



St. 181. Schollaert Channel, Palmer Archipelago, 160-335 ^^-y rnud, 5 specimens. 



St. 1660. Ross Sea, 74° 46-4' S, 178° 23-4' E, 351 m., 18 specimens, R 20 to R 76 mm. 



St. 1957. Off south side of Clarence Island, South Shetlands, 785-810 m., 11 specimens. 



The largest specimen (St. 181) has R 1 10 mm., r 18 mm., R = 6-i r; br at interradius 

 20 mm., at fifth superomarginal, 15 mm. Ludwig's largest specimen had R 78 mm., 

 while Koehler's measured R 54 mm. 



Ludwig has described this species in great detail. Koehler has supplied notes on 

 variations as well as very useful photographic figures. 



In his second paper, Ludwig (1910, p. 453) contrasts gerlachei with the much older 

 hirsutus of Studer, of which he had two specimens. According to this synopsis hirsutus 

 has a double circlet of smaller spinelets surrounding the central spine of the paxillae, 

 unequal ventrolateral spinelets, and pedicellariae on the ventrolateral plates only. 

 Gerlachei has a single circlet of paxillar spinelets, equal ventrolateral spinelets, and 

 pedicellariae on the ventrolateral as well as on other plates. 



In the Discovery specimens the first character holds fairly well, but some of the larger 

 plates of disk of biggest specimen have a second circle, or extra spinelets within the 

 single circle. This specimen has mtequal actinal intermediate (ventrolateral) spines. To be 

 more precise an elongate central spine is surrounded by smaller, unequal secondary 

 spinules. This disparity is exhibited by the smallest specimen, R 20 mm., St. 1660. In 

 the largest specimen there are numerous large pectinate pedicellariae on actinal inter- 

 radial areas, especially adjacent to adambulacrals, which are continued far along ray 

 between the inferomarginals ; but in three other examples (R 33 to R 55 mm.) the pedi- 

 cellariae are confined to actinal interradial areas (sometimes only one pedicellaria to an 

 area). 



Ludwig states in the same synopsis, that both hirsutus and gerlachei diff^er from teres in 

 having one inferomarginal spine while teres has two. The largest specimen (R 1 10 mm.) 

 has regularly 2 inferomarginal spines, the longer of which near base of ray, measures 

 8 mm., and the shorter 4 or 5 mm. Two other specimens also have the second spine 

 developed. 



