'54 



ECHINOIDEA. I. 



decidedly follow v. Marenzeller in this, and further draw the consequence of it (what has not 

 expressly been done by v. Marenzeller), viz. that Ech. iiorvcgicus becomes synonymous with 

 Ech. acutus. 



I shall here give the characters of the three most marked forms or varieties; but it is expressly 

 to be observed that all possible transitional forms are found, so that it will often be impossible to 

 decide, to which of these varieties some particular specimens are to be referred. 



Van mediterranea (PI. II. Fig. 8. PL XV. Figs. 14-15. PI. XVIII. Figs. 56. PI. XIX. Fig. 36). 

 The test high, conical, or more globular, somewhat flat, however, on the actinal side. The peri- 

 stome rather small, with the edge somewhat curved inward. The tubercles very small, considerably 

 smaller than in van Flemingii (comp. PI. XV. Fig. 15 with PI. XVI. Fig. 2; both figures are drawn in 

 natural size, the former [van mediterranea] accordingly from a much larger specimen than the latter 

 [van Flemingii]). As usual they are largest at the ambitus, and decrease evenly in size towards the 

 mouth and the apical area. The primary tubercles of the ambulacral areas form regular longitudinal 

 series, but, apart from some smaller irregularities, they are only found on every other ambulacral plate; 

 the secondary tubercles form no distinct longitudinal series. In a considerable part of the middle of 

 the test the pores recede not a little from the outer edge of the area, leaving a very distinct naked 

 space between the pores and the edge, generally quite without spines. The primary tubercles of the 

 interambulacral areas are somewhat larger than the ambulacral ones; also here they are not rarely- 

 wanting on every other plate for a longer or shorter way on the abactinal side. The secondary- 

 tubercles are small and rather few; on the actinal side some of them are almost as large as the 

 primary ones, and form a tolerably distinct longitudinal series inside of the primary series, and in the 

 largest specimen in hand one more series is indicated inside of these. The tubercles outside of the 

 primary series are placed quite irregularly. 



The spines on the abactinal side are rather few, short, and thin, those at the ambitus, however, 

 being longer and stronger; the latter are directed downwards like those on the actinal side, and the}' 

 are of such a length, that all the spines on the lower side reach equally far down with the point so 

 as to produce a quite even ambulatory surface (PI. II. Fig. 8); they are truncate, flat, and widened at the 

 point. The colour of the test is reddish, with more or less distinct, white stripes between the series of 

 tubercles; the actinal side white. The spines on the abactinal side are most frequently red or reddish 

 brown at the base, and white in the other part; of the actinal spines the outer ones are also red at 

 the base, and then white for a greater or smaller part, but thereupon a greater part of the point is 

 deep red, which gives to the animal a very peculiar appearance (PI. II. Fig. 8). The innermost ones, 

 nearest the mouth, are quite white. 



Van Flemingii (PI. I. Fig. 7. PL II. Fig. i. PL XVI. Figs. 2, 10, 16, 18. PL XVIII. Fig. 14. PL XIX. 

 Fig. 32. PL XXI. Figs. 25 26). The test most frequently somewhat conical, sometimes more flat; the 

 actinal side rather flat, the edge of the mouth only slightly bent inward; the peristome rather large. 



The tubercles large and strong. A primary tubercle is only found on every other ambulacral 

 plate; the plates where it is wanting, have generally two strong secondary tubercles, one out at the , 

 pores, and one nearer the median end, accordingly one on either side of the primary series of tubercles. 

 Most frequently every other plate is regularly wanting a primary tubercle, but it may be wanting in 



