ATLANT. DEEP-SEA EXPED. 1910 VOL. Ill] 



ECHINODERMATA 



21 



from 1° 47' to 45° 26' N., 2995—4700 m., bottom temp. 

 2.56°— 3.3° Cel. 1 ). 



R r 



r ' R 



mm. mm. 



P. subtilis "Michael Sars" 10 4 1 : 2.5 



„ strictus "Talisman" 17 5 1 : 3.4 



„ cylindratus "Challenger" 30 8. 5 1 : 3.53 



— „ — — „— 51 12.5 1 : 4.08 



„ subtilis "Blake" 60 12 1:5 



„ formosus "Albatross" 74 18 l:4.n 



„ elongatus "Talisman" 87 18 1 : 4.83 



The foregoing list of specimens of which measurements 

 exist, shows that older fully-developed individuals are 

 more long-armed than very young ones, for while R of 

 the smallest specimen was 2.5 r, it was 4 - - 5 r in the 

 larger specimens. 



Mediaster stellatus Ed. Perrier. 



Mediaster stellatus Ed. Perrier, Mem. Soc. Zool. de France, vol. 4, 



1891, p. 268. 



3 %. Stat. 70, 42° 59' N, 51° 15' W., 1100 m., temp. 3.7° Cel. 



Five specimens, measuring: 



mm. mm. mm. mm. mm. 



Arm-radius 32 38.5 47 48 54 



Disc-radius 12.5 14 17 16.5 16 



Breadth of arm in the middle 4.5 4.5 6 7 7 

 Breadth of paxillar area in the 



same place 2.5 2.5 4 4.5 5 



r:R 1:2.56 1:2.75 1:2.76 1 ; 2.91 1:3.37 



Number of dorso-marginal 



plates 23 28 30 29 31 



Number of ventro-marginal 



plates 24 28 29 29 31 



The specimens agree with the description and 

 illustrations which Perrier 2 ) gives of this species. The 

 adambulacral plates bear three rows of papillae with 4 

 to 6, most commonly 5 papillae in each row, of which 

 the furrow-papillae are the largest. The papillae of the 

 outermost row agree in size and form with the granules 

 of the adjacent actinal plates. The larger paxillae of the 

 abactinal plates bear 22 to 54 granules, but pedicellariae- 

 bearing paxillae have at most 20 granules. The pedicel- 

 lariae are more numerous in the larger specimens, than 

 in the smaller ones, thus evidently increasing in number 

 with the age of the animal. 



Mediaster stellatus is known only from the great 

 depths south and east of New-Foundland where it was 

 previously taken by the Prince of Monaco in 1887 at a 

 station north-east of the "Michael Sars" locality (stat. 161, 

 46° 4' 40" N, 49° 2' 30" W., 1267 m). 



Astrogonium fallax Ed. Perrier. 



(PI. 5, fig. 1). 



Astrogonium fallax Ed. Perrier, Ann. Sci. Nat., ser. 6 tome 19, 1885, 



no. 8, p. 37. 

 30 h. Stat. 70, 42 : 59' N., 51° 15' W., 1100 m. temp. 3.7 Cel. 



Two specimens measuring: 



Arm-radius 37 mm. 46 mm. 



Disc-radius 11 „ 14.5 „ 



Breadth of arm in the middle 5.3 „ 6 . 



Breadth of paxillar area in the same place 2.2 „ 3 „ 



r : R 1 : 3.36 1 : 3.17 



Number of dorso-marginal plates 29 35 



Number of ventro-marginal plates 29 35 



The largest specimen agrees with Koehler's figure 

 of this species. 1 ) In the smallest specimen some few of 

 the ventro-marginal plates only have rudimentary spiny 

 formations, the rest exhibit a scale-like granulation 

 similar to that of the largest individual. The small 

 specimen has likewise a similar armature of the adam- 

 bulacral plates and similar uniform granulation of the 

 plates of actinal area. I have therefore referred the 

 smallest specimen also to Astrogonium fallax. 



Astrogonium fallax was first found by the "Talisman" 

 at 4 stations off the Azores, 1440 -- 2220 m., and there 

 it was also later taken by the Prince of Monaco at two 

 stations, 1165 -- 1385 m. Verrill 2 ) further records it from 

 the east coast of North America; but judging from Verrill's 

 figures, this North American form appears to differ from 

 the typical Astrogonium fallax. The uniform crowded 

 granulation of the plates in the actinal area is characteristic 

 of this species, while Verrill's drawing (fig. 2 a) exhibits 

 a more scattered granulation, and the individual granules 

 vary in sizes, a circumstance which was, however, also 

 pointed out by Koehler. 



Pentagonaster dentatus Ed. Perrier. 



Pentagonaster dentatus Ed. Perrier, Nouv. Arch, du Museum d'Hist. 



Natur., ser. 2 tome 6, 1883, p. 242, tab. 8, fig. 3. 



Vs. Stat. 24, 35° 34' N., 7° 35' W„ 1615 m., yellow mud, temp. 

 8° Cel. Two specimens. 



%. Stat. 25 B, 35° 46' N., 8° 16' W., 2055 m., yellow mud. 

 Three specimens. 



23 /s. Stat. 41, 28° 8' N., 13° 35' W„ 1365 m., yellow mud, 

 temp. 6° Cel. Six specimens. 



27 A. Stat. 95, 50° 22' N., 11° 44' W., 1797 m., temp. 3.5° Cel. 

 A large specimen. 



The specimens were measuring in millimetres: 



'). "Challenger" 2.6°, "Albatross" 3.3° (3 stations) and 2.8° 

 (one station) "Michael Sars" 2.56°. 



2 ). Ed. Perrier: Stellerides, Res. Camp. Sci. Monaco, Fasc. 11, 

 1896, p. 46, tab. 4. figs. 1 — 1 d. 



'). Koehler: Echinodermes, Res. Camp. Sci. Monaco, Fasc. 34, 

 1909, p. 71, tab. 18, fig. 2. 



2 ). Transact. Connecticut Acad., vol. 10, 1899, p. 190, tab. 30, 

 figs. 2 — 2 b. 



