ATLANT DEEP-SEA EXPED. 1910 VOL. Ill] 



ECHINODERMATA 



19 



which therefore to a still higher degree is a warm-water 

 species, but which was nevertheless taken three times in 

 the cold area of the Faroe-Shetland Channel. 



Psilasteropsis patagiatus Sladen. 



Psilaster patagiatus Sladen, Asteroidea, Rep. Sci. Res. Challenger 

 Zool., vol. 30, 1899, p. 232, tab. 7, figs. 11 & 12, tab. 41, figs. 3 & 4. 

 Vs— Vs. Stat. 101, 57° 41' N., 11° 48' W., 1853 m, hard clay, 

 temp. 3.3° Cel. One specimen, measuring: 



Arm-radius -. 92 mm. 



Disc-radius 30 „ 



Breath of arm at base 36 „ 



Number of dorso-marginal plates 34 „ 



r : R 1 : 3.07 



A : R 1 : 2.56 



In the type specimen of this species the proportion 

 r : R was 1 : 3.95 and A : R = 1 : 4.05., Koehler found in 

 some large specimens from the collections of the Prince 

 of Monaco the proportions r : R to vary between 1:4.18 

 and 1 : 4.72. The specimen under discussion is remarkable 

 for its comparatively short and broad arms. It differs 

 further from the type specimens by a more abundant 

 spiny armature of the ventro-marginal plates, in as much 

 as some of the plates of the arm-angles bore up to 10 

 spines, which recalls the armature observed in a few 

 specimens of Psilaster andromeda from stat. 101. The 

 specimens agree in other respects with the description 

 and figures of Psilasteropsis patagiatus given by Sladen. 

 17 furrow papilla? were present on the middle adam- 

 bulacral plates. 



The type specimen was captured by the "Challenger" 

 off the Cape Verd Is. The "Princesse Alice" also took 

 it there, as well as off the coast of Morocco, at the Canary 

 Is., the Azores and in the Bay of Biscay. The "Hirondelle" 

 and the "Talisman" likewise collected it within the same 

 area, though the exact localities can not be given, Perrier, 

 as above stated, having confused the species with Psilaster 

 andromeda. The "Helga" captured it off Ireland. The 

 "Michael Sars" locality lies to the west of the Hebrides. 

 Thus Psilasteropsis patagiatus is an East Atlantic species, 

 ranging from 16° 34' to 57° 41' N. Bathymetrical 

 distribution 1095—2165 m. 



Dorigona arenata Ed. Perrier. 

 (PI. 4, figs. 5—8). 



Pentagonaster arenatus Ed. Perrier, Bui. Mus. Comp. Zool, vol. 9, 



1881, p. 21. 



Vs. Stat. 21, 35° 31' N., 6° 35' W., 535 m., yellow sand, ternp. 



11.52° Cel. Three specimens, of which the two best preserved 

 ones measured: 



Arm-radius 88.5 mm. 90 mm. 



Disc-radius 19 21 



Distance of the madreporic plate 



from centre of disc 4 mm. 4 mm. 



Size of the madreporic plate 2.5 X 2 „ 2.5 X 2.5 , 



r : R 1 : 4.66 1 : 4.29 



Number of dorso-marginal plates 37 32 



Number of ventro-marginal plates.... 39 39 



The dorso-marginal plates are joined together, beginning with 

 the 5th or 6th plate. 



Perrier states that pedicellariae are wanting in the 

 marginal plates of this species 1 ). I found pedicellariae pre- 

 sent, however, on the dorso-marginal as well as on the 

 ventro-marginal plates of the three specimens mentioned 

 above, but the number of pedicellariae-bearing plates 

 seems to vary considerably in the different individuals 

 In one of my specimens pedicellariae were present on 6 

 dorso-marginal and on one ventro-marginal plate, in an 

 other specimen on 71 dorso-marginal and on 67 ventro- 

 marginal plates and in the third specimen on 89 dorso- 

 marginal and on 116 ventro-marginal plates. I ought to 

 mention that one or more of the arms of all the specimens 

 were defective, which admits the possibility that the 

 number of pedicellariae-bearing plates might have been 

 greater if the specimens had been intact. Most of the 

 plates of the interbrachial angles were furnished with 

 pedicellariae. They may also, though more rarely, be 

 found on the arm plates, particularly in the distal half 

 of the arms, but in the outermost plates they appeared 

 to be constantly absent. The majority of marginal plates 

 bear one pedicellaria, but both the dorso-marginal and 

 the ventro-marginal plates may have two or very rarely 

 three pedicellariae. 



Pedicellariae are wanting in the inter-radial actinal 

 area. On the abactinal surface they are restricted to the 

 papularium and are besides, as regards number, apparently 

 subject to great individual variations. Only 6 pedicellariae- 

 bearing plates were counted in the first of the specimens 

 in question, 28" in the second, and 8 in the third. None 

 of the plates bore more than one pedicellaria, and most 

 of these were situated near the margin, only exceptionally 

 farther in on the plate, as is normal in the marginal 

 plates. As in Pentagonaster granulans the pedicellariae 

 are composed of two rounded quadrate flaps about 0.64 

 mm. long and about O.23 mm. broad. Those on the 

 marginal plates have the same form, but are somewhat 

 smaller. 



The mouth-plates carry 6—8 papillae and the adjacent 

 adambulacral plates have 4—5 furrow-papillae. The 

 number of adambulacral papillae is 6 to 7 in the middle 

 of the arm and up to 9 in the outer half of the arm. 

 Behind the furrow-papillae there are three and, at the 



'). Ed. Perrier: Echinodermes, Exp. Sci. du "Travailleur" et du 

 "Talisman", 1894, p. 379. 



