[INOIDEA. II. 



7' 



the same as the P.phiale of Wyv. Thomson from the Rockall Channel, 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. Urechinus naresianus.) 



This species was taken by the Ingolf at the following stations: 



St. 11. (64° 34' Lat N. 3 1° 12' Long. W. 1300 fathoms 1 6 C. Bottom temp.). 2 specimens. 



— 40. (62° 00' 21" 36' S45 — 3°$ — — ) 1 



-83. (62 25' - 28 30' 9 i 2 3° 5 _ , 1 _ 



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

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

 metrical range, as hitherto known, is S45 — 1975 fathoms. 



The very interesting morphological relations of the bivium show that P.phiale is really one 

 of the more primitive Pourtalesi;e, in spite of its modified form. The continuity of the ambulacra I 

 and V it has in common with Sternopatagus and Pourtalesia carinata, which latter species through 

 its two pores in the plates I. a. 1 and V. b. 1 as well as by its large labrum, maintains the place as 

 the least modified of the Pourtalesia-species, (viz. among those species whose structure of the test is 

 thus far known) 1 . Otherwise important light is thrown on the structure of P. carinata by what has 

 here been made known of the structure of the actinal part of the test in P. pkiale. A comparison of 

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

 Pourtalesia shows almost beyond doubt that the plates named by Loven 5. a. 2 b. 2 and V a. 2 b. 2 

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

 in P. pkiale; but in case that plate is really Y. a. 2, which can scarcely be doubted, the plate named 

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

 To be sure, it is separated from the plate V. b. 1, by the corner 

 of the labrum; but the connection between these two plates in 

 P. phiale is already so very narrow, that it is very easily con- 

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

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

 Loven's Figure thus becomes a plate of interambulacrum 4. 

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

 interpretation of the plates for the direct comparison with P.phiale 

 Figs. 11 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 verv important conclusion that Pourtalesia carinata is Fig. n. I'art of 

 not amphisteruous as thought bv Loven as the result of his, actinal plastron 



of Pourtalesia 



evidently wrong, interpretation 2 of the plates in this figure, but phiale. 



1 De Meijere iSiboga Echin. PI. XXI. 41S p. 1681 represents Echinocrepis cuneata as having the same structure of 

 the bivial ambulacra, founding his opinion on PI. XXXV. a. 10 of the Challenger* -Ech. Echinocrepis seligera has its bivial 

 ambulacra separated by the interambulacra 1 and 4 (Panamic Deep-Sea Echini. PI. 67. 1, Fig. 167I. Also the apical system is 

 verv different in these two species, compact in Ech. cuneata, disconnected in Eih. setigera. It can then scarcely be doubted 

 that the latter species was unrightly referred to the genus Echinocrepis and will have to be made the type of a new genus. 

 1 Comp. below p. 83— 84.) 



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.phiale, Loven could scarcely interpret these plates in P. carinata otherwise. 



Fig. 12. Part of actinal 

 plastron of Pourtalesia 

 carinata after Loven. 



