28 



JAMES A. GRIEG 



[REP. OF THE "MICHAEL SARS" NORTH 



must be regarded as typical for this form. Judging from 

 Verrill's figure 1 ) the form of L. furcifer occurring off the 

 east coast of North America is of similar appearance. In 

 specimens from Arctic regions on the other hand the arc 

 is most often wide and rounded, and the arms broad at 

 base tapering rapidly toward the point. This is evidently 

 the form on which Fisher based his remarks on L. furcifer 

 and it is also the form depicted in works on Arctic echino- 

 derms. Judging, however, from the material at my disposal, 

 the form of the arc seems to be subject to variations and 

 this is moreover borne out by the literature on the sub- 

 ject. Duncan and Sladens figure of L. furcifer-) has but 

 slightly rounded arcs. In two specimens in the Kara Sea 

 bv the Duke of Orleans they are a little more rounded 

 and this is more particularly the case in the individual 

 from the cold area of the Norwegian Sea illustrated by 

 Danielssen and Koren 3 ). In a specimen from Gaasefjord, 

 Jones Sound they are extremely wide and rounded' 4 ). 

 There are, however, Arctic specimens, which differ very 

 little in their form from the Boreal. This is the case 

 with the L. furcifer from the cold area of the Faroe — 

 Shetland Channel figured by Wyville Thomson in "The 

 depths of the Sea" (p. 119, fig. 14). A very extreme 

 example of such Arctic forms is presented by the speci- 

 mens which I illustrated on "Michael SarsAsteroidea"(p.71, 

 fig. 9). It reminds one of L. fucilliger vexator, a fact 

 which Fisher likewise calls attention to. 



The abactinal skeleton of the Arctic furcifer consists 

 of stellate deposits which are united so as to form a 

 meshwork. Its structure appears, however, to be subject 

 to great variations. In some individuals the deposits are 

 close up to one another, so that the meshes become 

 small and narrow, in other examples, such as one from 

 Jones Sound, the deposits are isolated. Between these 

 two are all shades of intermediary forms and also a mesh- 

 work like that which characterices vexator (cfr. Fisher 

 pi. 114, fig. 2 b). In the Arctic furcifer the paxillae are 

 more scattered than in the boreal form, and they are 

 larger, more robust and have longer spines. We may 

 find examples whose paxillae closely resemble those of 

 vexator. The same is true of the actinal paxillae and 

 the adambulacral armature. With abundant material of 

 the Atlantic Lophaster at hand, it will not be possible to 

 distinguish it from the Pacific form. Fisher mentions 

 intermediary forms between L. furcilliger and L. furcil- 



1 ) Verrill: Res. Explr. made by the Steamer „Albatross" in 1883, 

 1885, tab. 16, fig. 49. 



2 ) Duncan & Sladen: Mem. on the Echinodermata of the Arctic 

 Sea to the West of Greenland, 1881, tab. 3, fig. 9. 



: ) Danielssen & Koren: Asteroidea, 1884, tab. 8, fig. 12. 

 •) Grieg: Echinodermata, Rep. II Norweg. Arctic Exp. in the 

 "Fram" 1898—1902, no. 13, 1907, tab. 3, fig. 1. 



liger vexator and my material shows transition forms 

 between the latter and L. furcifer. I therefore fully agree 

 with Mortensen in considering furcilliger and vexator as 

 hardly more than varieties of L. furcifer. To the varieties 

 of this species we must possibly also refer Sarkaster 

 validus Ludwig 1 ) which was taken by the "Albatross" 

 in 1891 between Galapagos Is. and Las Tres Marias Is., 

 523 — 1244 m., and which as already pointed out by 

 Fisher, is a Lophaster and presents agreements with L. 

 furcilliger. 



Pteraster reductus Koehler. 

 PI. 5, figs. 6, 7. 



Pteraster reductus Koehler, Bull. Inst. Oceanogr. Monaco, 

 no. 99, 1907, p. 23. 



8 /c, stat 53, 34°59'N. 33° V W., 2615— 2865 m., yellow hard 

 clayey mud, temp. 3 Cel. Three specimens of which the best pre- 

 served measured: 



Diameter ' 37 mm. 



Arm-radius 20 „ 



Disc-radius 15 „ 



Disc-radius measured on the actinal side to the 



marginal suture 12 „ 



Height 12 „ 



Greatest breadth of arm 17 „ 



Greatest breadth of arm measured on the act- 

 inal side between marginal sutures 14 „ 



Greatest breadth of the actino lateral area.... 5 „ 



Number of actino-lateral beams 15 „ 



r: R 1 : 1.33 „ 



In the two other specimens which are somewhat 

 defective the arm-radius measured 22 mm. and 27 mm., 

 respectively, disc-radius 13 mm. and 18 mm., greatest 

 width of arms 16mm. and 20mm., r:R= 1 : 1.69 and 1 : 1.5. 



Arms broad at base, tapering rapidly. Abactinal sur- 

 face considerably arched, the actinal plane. Supradorsal 

 membrane thin and fibrous. Paxillae numerous, compact 

 and furnished with cluster of some 20 long thin calca- 

 reous spinelets. Of the actino-lateral beams the third is 

 longest. In the 37 mm. specimen it is 7 mm. long. 



The tube-feet are large and present a paired arrange- 

 ment in two rows. The innermost adambulacral plate 

 has 6 papillae, the remainder 5. These papillae are united 

 by a membrane and arranged in slightly curved, trans- 

 verse rows, similarly as in Pteraster personatus Sladen 2 ). 

 The innermost papilla is 1 — 1.5 mm. in length, the outer- 

 most 3 — 4 mm. The mouth plates are well-developed 



') Mem. Mus. Comp. Zool. vol. 32, 1905, p. 185, tab. 15, figs. 

 75 & 76, tab. 29, figs. 171—173, tab. 30, figs. 174—177. 



2 ) Proceed. R. Irish Acad., ser. 3, vol. 1, 1890, p. 694, tab. 27, 

 figs. 1—5. 



