168 PAXAMIC DEEP SEA ECHIXI. 



The actinal system of P. Rathhuni (Pis. 81, fig. 1 ; 83, fig. 1 -, 85, figs. 1, 

 2) is somewhat pentagonal, Fig. 240, placed in the centre of a similarly 

 shaped depression which extends to the fourth or fifth ambulacral plate (Pis. 

 83, fig. i; 85, fig. i). The actinostome is subcentral, nearer the ambital 

 edge, and surrounded by a couple of inner rows of irregularly shaped polyg- 

 onal or elongated plates covered by miliaries, while on the outer edge are 

 ten large pointed pentagonal plates which form a closed circle, recalling the 

 buccal plates of Paloeostoma (PL 85, figs. 1, 2). Seen from the inside the 

 edge of the actinostome is strengthened by a circular keel forming the edge 

 of the actinal plates of the corona. 



The rudimentary phyllodes extend to the eighth or ninth ambulacral plate. 



Station 3360, southwest of Mariato Point, in 1672 fathoms. Lat. 6 17' 

 N. ; Long. 82' 5' W. Bottom temperature 36^4. Fn. bk. drk. gn. s. 



Station 3374, southwest of Malpelo Island, in 1823 fathoms. Lat. 2' 35' 

 N. ; Long. 83"^ 53' W. Bottom temperature 36°.4. Gn. ooze. 



Bathymetrical range, 1672-1823 fathoms. Temperature, 36^4. 



PALEOPNEUSTIDiE A. Ag. 



Pal^otropus Lov. 

 Palseotropus Loveni A. Ag. 



Palaeotropus Loveni A. Ag., Proc. Am. Acad. 1879, Vol. XIY, p. 204. 



Palgeotropus Loveni A. Ag., "Challenger" Echiuoidea, 1881, p. 158, PI. XXT, figs. 3-16. 



Plate 87. 



The figures of this species given in the " Challenger " Echinoidea are 

 scarcely distinct enough to give them sufficient accuracy. In order better 

 to characterize this genus, which has affinities to so many of the ancient 

 types of the deep-sea genera, and also to many well-known recent Spatan- 

 goids, I have given on Plate 87 a number of figures of Pakvotropus Loveni 

 which will materially assist in following tlie description of the genus and 

 species given in the " Challenger." 



Seen from the actinal side (PI. 87, fig. -/), the contrast between the 

 bare ambulacra, especially the broad posterior lateral ambulacra, and the 

 interambulacra, closely tuberculated except towards the actinal systeni, is 

 most marked. 



The rudimentary phyllodes extend only for two or three ambulacral 

 plates (PI. 87, figs. /, 5). 



