146 



ECHINOIDEA. I. 



13. Echinus Alexandri Dan. Kor. 



PI. V. Figs. 2— 3, 5—7. PI. XV. Figs. 13, 17. PI. XVI. Fig. 8. PI. XVIII. Figs. 9, 11, 19, 23, 25. PI. XIX. Figs. 16, 31, 34, 38. 



PI. XX. Figs. I, 2, 27. PI. XXI. Figs. iS— 20, 27. 



Literature: DanieLssen & Koren (109). — Daiiielssen (iio): Echinida. Nor.ske Nordhavs- 

 exped. p. I. T. I. — Koehler (224—226): Echinodermes. «Caudan\ p. 92. PI. I. fig. 4 PI. II. fig. 18— 19. 



Of this large, fine species we have a very great material from the -Ingolf , and as I have had 

 the type specimen of Dan i el s s en for examination, I have been able to identify it with certainty. 

 Prof. Koehler has further sent me some of his specimens from .Caudans, so that I am also able to 

 corroborate the correctness of his determination. On the basis of this o-reat material I shall then eive 

 a new description of the species. 



The test is much flattened, the height generally a little less than half the diameter of the test; 

 specimens of a middle size and smaller ones are qnite flat above, the larger ones a little ronnded. The 

 actinal side is flat, not at all or vers- little curved inward at the edge of the month. The slits as 

 usual small and rather indistinct. 



All the measures in milUmetres. 



The anibnlacral areas (PL XV. Fig. 13) in large specimens scarcely half as broad as the inter- 

 ambnlacral areas, in smaller specimens a little more than half this breadth; at the edge of the mouth 

 the two areas are of abont eqnal breadth. The number of compound piates in the anibnlacral areas 

 is only abont '/a— V; time greater than that of the interambulacral areas, accordingly the ambulacral 

 piates are rather high. The arcs of pores are not placed ver)- obliqnely, in small specimens they are 

 almost perpendicular. In the type specimen the arcs of pores show a remarkable irregularity, as is 

 seen in the figures of Danielssen. As no similar feature is seen in any of the Ingolf-specimeus it is 

 no doubt something abnormal. The pores reach quite to the edge of the piates. The boundaries 

 between the small piates rather indistinct, the boundar)- line between the areas rather highly sinuate. 

 The primary tubercles form a very conspicuous, dense longitudinal series; a primar\- tubercle is found 



