E ch i n i da, 



Echinus Alexandri '. Dan. et Kor. 



Tab. I. 



Forelobig er denne smukke Echinide beskrevet at' min 

 afdode Ven Koren og mig i „Nyt Magazin for Naturviden- 

 skaberne, 27 B., Side 294, 1883. 



Skallet {P&risomay er nedtrykt, 45*"'" høit, 86""" i 

 Diameter. Periferien (Awbifus) er lidt femkantet med 

 stumpe Kanter. Mimdmembranen (Adinostoma) er 23""" i 

 Diameter, tyk og tæt besat med Pedicellarier. Skallets 

 Plader ere ikke meget boiede, men temmelig brede. Tab. 

 I. Fig- 1, 2. 



Interambulacralpladerne bære en stor primær Tuberkel, 

 der rager op fra en ringformig Fordybning, hvis Rand er 

 omgiven af 6 — -7 sekundære Knuder, Tab. I, Fig. 3 a. Paa 

 den primære Tuberkels ydre Side (den nærmest Ambulacral- 

 poferne) er der paa de fleste Plader. naar undtages de 

 nærmest Mundmembranen og Analfeltet, 4 temmelig store, 

 sekundære Tuberkler, Tab. I, Fig. 3 b, som staa uregelmæs- 

 sigt, og paa dens indre Side 1' — 3 lignende, Tab. I, Fig. 3c. 

 Imellem disse sekundære Tuberkler gruppere sig mange 

 større og mindre Miliartuberkler. De primære Tuberkler. 

 der er størst paa Periferien og aftage i Størrelse mod 

 begge Ender, danne en regelmæssig Længderække, Tab. I, 

 Fig. 3. 



Ambulacralpladerne bære ligeledes en primær Tuber- 

 kel, der dog er langt mindre end den paa Interambulacral- 

 pladerne, er stillet i en Længderække og aftager saa be- 

 tydeligt i Størrelse mod Analfeltet, at den paa de øverste 

 Plader neppe har Omfanget af en liden, sekundær Tuberkel, 

 Tab. I, Fig. 3 d. Der er dog enkelte Ambulacralplader, 

 hvor de primære Tuberkler mangle ganske. Til Siderne 

 af den primære Tuberkel sees en og to sekundære, en paa 

 den udvendige og to paa den indvendige Side, men 

 heller ikke dette er konstant; imellem de sekundære Tu- 

 berkler tindes mange, uregelmæssigt stillede Miliartuberkler, 

 Tab. I, Fig. 3. 



E ch i n i da. 



Arten er benævnt efter den berømte "amerikanske Naturforsker. 



Professor, Dr. Alexander Agassiz. 



Den norske Nordhavse.xpedition. D. C. Danielssen: Echinida. 



Echinus Alexandri '. 



pi. i. 



Dan. et Kor. 



This beautiful Echinid has been precursorily described 

 by my deceased friend Koren and myself in „Nyt Magazin 

 for Naturvidenskaberne", Vol. 27, page 294, 1883. 



The shell (perisoma) is flattened, 45""" in height, 86""" 

 in diameter. The periphery (anibitus) is slightly pentagonal, 

 with Idunt edges. The oral membrane (actinostoma) is 

 23'""' in diameter, thick and closely beset with pedicellaria. 

 The plates of the shell are not much curved, hut pretty 

 broad (Pl. I, figs. 1, 2). 



The interambulacral plates carry a large primary 

 tubercle, which projects upwards from an annular depression 

 whose margin is surrounded by 6 — 7 secondary nodules 

 (Pl. I, fig. 3 a). Upon the outer side of the primary 

 tubercle (that next the aml)ulacral pores) there are found 

 on most of the plates, except those nearest to the oral 

 membrane and the anal area, 4 rather large, secondary 

 tuhercles (Pl. I, fig. 3 b), placed irregularly ; and upon the 

 inner side 1 — 3 tubercles similar to those illustrated on Pl. 

 I, fig. 3 c. Bet"ween these secondary tubercles there are 

 grouped many larger and smaller miliary tubercles. The 

 primary tubercles, which are largest on the periphery and 

 diminish in size towards both extremities, form a regular 

 longitudinal series (Pl. I, fig. 3) 



The amlmlacral plates likewise carry a primary 

 tubercle, which is, however, much smaller than the one on 

 the interambulacral plates, is situated in a longitudinal 

 series, and diminishes so considerably in size towards the 

 anal area that, on the uppermost plates, it is barely the 

 size of a small, secondary tubercle (Pl. I, fig. 3 d). There 

 are, however, a few ambulacral plates in which the primary 

 tubercle is entirely awanting. At the sides of the primary 

 tubercle there are visible one and two secondary ones, 

 one on the outer and two on the inner side, but neither 

 is that feature a constant one; betvveen the secondary 

 tubercles there are many irregularly placed miliary tuhercles 

 visible (Pl. I, fig. 3). 



1 The species is designatet! after the celebrated American naturalist. 

 Professor, Dr. Alexander Agassiz. 



] 



