144 



ECHINOIDEA. I. 



small plates; here and here a tubercle may be found on a somewhat larger plate. Nearest to the 

 anal opening the small plates are a little lengthened. 



The buccal membrane commonly richly provided with large, simple fenestrated plates as in 

 Ech. Alexandri; those inside of the bnccal plates also as in this species. Bihamate spicnles may be 

 found in rather great number among the fenestrated plates. A few of the plates outside of the buccal 

 plates are larger and somewhat complicate, and carry pedicellarise. No spines on the buccal plates. 



The spines of a middle length, : /z 2 /s f the diameter of the test, rather strong; they are 

 largest at the ambitus, but decrease generally only little towards the apical area. The actinal prim- 

 ary spines may be truncate and flat at the point (not constantly), not irregularly widened as in 

 Ech. acutus. 



The pedicellarise are generally very numerous, especially the ophicephalous ones. The globi- 

 ferous ones (PI. XVIII. Figs. 2 3) have most frequently 2 3 teeth on either side of the blade, some- 

 times 3 or only one on one side, two on the other. The basal part has often a few indentations in 

 the edge, but this is no constant feature. The stalk is rather strong and may at the upper end have 

 some thorns directed downward (PI. XX. Fig. 23). The tridentate pedicellarise (PI. XVIII. Figs. 22, 26. 

 PI. XX. Fig. 9): the valves rather broad, a little widened at the point, where they join; the edge is here 

 rather sinuate, in the other part it is straight, thick, and set with small teeth forming somewhat 

 irregular transverse series. There is a rather well developed mesh-work at the bottom of the blade. 

 - Together with this form is often found a smaller one (PI. XX. Fig. 9), where the blade is almost 

 quite flat and rather abruptly truncate at the point, without mesh-work. In some specimens only this 

 form is found. Transitional forms between this form and the larger one are found, so that it cannot 

 be regarded as another kind than the larger form. - The ophicephalous (PI. XIX. Fig. 10) and the 

 triphyllous pedicellarise (PI. XX. Fig. 22) show no marked peculiarities. - The sphseridiae (PI. XIX. 

 Fig. 26) are generally somewhat grooved and thorny; the grooves often form rather distinct longi- 

 tudinal series. The spicuies (PI. XX. Fig. 8) are small and rather varying in form. They are pretty 

 numerous in the tube feet and gills; in the skin round the base of the spines some spicuies are 

 generally found, and sometimes a few are found in the stalks of the pedicellarise (the globifer- 

 ous ones). 



The typical coloration is as on PI. III. Fig. 4: purple, white-tipped spines; the test white, 

 slightly rosy round the apical area (PI. I. Fig. 3). In some of the specimens in hand this colour, how- 

 ever, is only slightly indicated; some are quite white, others have only a slight yellowish red tint 

 around the apical area or only at the base of some of the primary tubercles on the abactinal side. In 

 one specimen the test is of a fine lilac colour (PL I. Fig. 2). 



Ingolf> St. i (6230'N. L. 82i'W. L. 142 fathoms, Sand, Shells. Bottom temp. 7 8). i spec. 

 -47(61 32' 13 40' 950 Mud. 3 i). 3 



- 52 (63 57' 13 32' 420 7 2). 2 



- 54 (63 08' 15 40' 691 4 2). 6 



This species is indigenous in the sublittoral-archibenthal zone of the northern Atlantic, both 

 at the European and American side, as well as south of Iceland, and in the sea along Norway; it is 

 found on ca. 50 950 fathoms. The statement that it goes down to 1350 fathoms ( Challenger - 



