ECHINOIDEA. II. 



71 



the same as the P. pliiali: of Wyv. Thomson from the Rockall Cliaunel, thus loses its interest from a 

 zoogeographical point of view, since in any case this species really occurs both in the Northern Atlan- 

 tic and in the Antarctic Sea. (Comp. Urechiiius iiarcsiiuius.) 



This species was taken b}' the Ingolf at the foUowing stations: 



St. II. (64° 34' Lat. N. 31° 12' Long. W. 1300 fathoms i°6 C. Bottom temp.). 2 specimen.s. 



40. (62° 00' 



21' 



^6' 



845 — 3°3 — - ) i - ' 



- 83. (62° 25' - 28° 30' - 912 _ 3°5 _ _ , I _ 



The geographical distribntion of the species is: Northern Atlantic (S. of Iceland, Denmark 

 Strait) and Antarctic Sea. It will doubtless be found to occnr all over the Atlantic Ocean. The bathy- 

 metrical range, as hitherto kno\vn, is S45 — 1975 fathoms. 



The very interesting morphological relations of the bivinm show that P. phialc is really one 

 of the more primiti\e Ponrtalesiæ, in spite of its modified form. The continuit\- of the ambulacra I 

 and \' it has in common with Sferiwpatagus and Poiirtalcsia carinata. which latter species throngh 

 its two pores in tlie piates I. a. i and W b. i as well as b\- its large labrum, maintains the place as 

 the least modified of the PourtaIrsia-?,^(tc\Q^^ (viz. among those species whose structure of the test is 

 thns far knownl'. Utherwise important light is thrown on the structure of P. carijiata \>\ what has 

 liere been made known of the structure of the actinal part of the test in P. phialc. A comparison of 

 the figure of the actinal side of P. pliialr (PI. VI. Fig. 7) with the PI. VI. Fig. 42 of Lovén's On 

 Pourtalesia .shows almost beyond doubt that the piates named by Loven 5. a. 2 b. 2 and \'. a. 2 b. 2 

 are wrongly interpreted. The plate named V. b. 2 is seen to agree very clo.selv with the plate V. a. 2 

 in P. pliinic : but in case that plate is really V. a. 2, which can scarcely be doubted, the plate named 

 b\- Loven 5. a. 2 really becomes the ambulacral plate V. b. 2. 

 To be sure, it is separated from the plate \'. b. i, by the corner 

 of the labrnm; but the connection between these two piates in 

 P. pliialt is already so ver\- narrow, that it is very easih' con- 

 ceivable how the total separation has been prodnced in P. carinata 

 by the great development of the labrum. The plate V. a. 2 in 

 Lovén's Figure thus Ijecomes a plate of interambulacrum 4. 

 I may give here a copy of the figure from Loven with niy 

 interpretation of the piates for the direct comparison with P.pliialc 

 Figs. II and 12). I think it will be agreed that my interpretation 

 thereof has all evidence of being the right one. But this leads 

 to the very important conclusion that Pourtalesia carinata is 

 not amphisternons as thought by Loven as the result of his, 

 evidently wrong, interpretation - of the piates in this figure, but 



Fig. r I. Part of 



actinal plastron 



of Pourtalesia 



phialc. 



Fig. 12. Part of actinal 

 plastron of Pourlalesia 

 carinata after Loven. 



1 De Meijere (Siboga Echin. PI. XXI. 41S p. 168) represents Echinocrepis cuneata as ha\-ing the same strncture of 

 the bivial ambulacra, founJing his opinion on PI. XXXV. a. lo of the Challenger»-Ech. Echinocrcpis setigera has its bivial 

 ambulacra separated bj- the interambulacra i and 4 (Panamic Deep-Sea Echini. PI. 67. i, Fig. 167). Also the apical system is 

 very different in these two species, compact in Ech. ctaieata, disconnected in Ech. .letigera. It- can then scarcely be doubted 

 that the latter -species was unrightl)- referred to the genus Echinocrcpis and will have to be made the type of a new genus. 

 I Comp. Iielow p. 83 — 84. 1 



- It is of course, the fragmentary condition of his material of this species which has caused that interpretation. Not 

 knowing the real structure of P. phialc. Loven could scarcely interpret these piates in P. carinata otherwise. 



