ECHINOIDEA. I. 



S a r s has it from 50100 fathoms ; the specimens taken by Dr. H. I. H a n s e n at Syracuse are from 

 2030 fathoms. The form mentioned from Florida is stated by Rathbun (336 p. 611) to be from 

 25 426 fathoms. 



3. Stereocidaris ingolfiana n. sp. 



PI. VI. Figs. I 5, II. PI. VIII. Figs. 4, 10, u, 16, 19-21, 23, 26, 28, 30, 36. PI. XI. Figs. 12, 16, 17, 23, 28, 30, 32, 33. 



PI. XVI. Fig. i. 



Diameter Height Diam. of the peristome Diam. of the apical area Longest spines 



35 mm. 27 mm. 14 mm. 15 mm. 



32 29 12 13 65 mm. 



28 17 10-5 10-5- 48 



27 20 10 - 13 62 



25 18 9 12-5- 47 



24 I7'5- 9 J 3 5 



16 10 6-5- 5 



9 6-5- 4 5 26 



As will be seen from the given measures the height of the test is rather varying. Nevertheless 

 the form is upon the whole very characteristic (PI. VI. Fig. 3). It is broader above than below ; the 

 upper side is generally very flat, and there is, about the middle of the first fully developed interambu- 

 lacral plate, a rather steep bending from the upper side to the almost perpendicular, below slightly 

 inward bent sides. Below at the edge of the peristome a rather abrupt bending is likewise found; the 

 two lowermost interambulacral plates are situated almost horizontally. 



The interambulacral areas are 3724 times as broad as the ambulacral areas; they consist of 

 57 plates. The areoles are deep, the edge round them raised, with a single circle of 1516 more 

 conspicuous tubercles; in large specimens these are more indistinct. The other part of the plates is 

 closely set with very small tubercles, which are in the larger specimens rather distinctly arranged in 

 irregular transverse rows; in smaller specimens this arrangement is not distinct. Even at the median 

 line where the plates join, a narrow naked stripe is scarcely seen, in the largest specimen not at all. 

 The plates sink somewhat down towards the median line and outward towards the pore area. Even 

 the lowermost areoles are separated by a rather broad space with distinct tubercles (PL XVI. Fig. i). 



The ambulacral areas: There are 1012 ambulacral plates for each interambulacral plate. 

 The pore area is half so broad as the middle part of the ambulacral area. The pores are only sepa- 

 rated by a narrow partition-wall; the outer pore is a little smaller. (In D. papillata and C. affinis the 

 pores are of equal size; in the latter there is a rather broad partition- wall between them) 1 ). The pri- 

 mary series of tubercles is only little conspicuous; besides the primary tubercle about 3 5 small 

 tubercles are found on each ambulacral plate, so that there is no trace of naked intervals; the whole 

 area between the series of pores therefore appears as a densely granulous stripe in which the bound- 

 aries between the separate plates are only seen with difficulty (PI. VI. Fig. n). 



The plates of the peristome are set with numerous small tubercles, but only on the free edge. 

 - The apical area (PI. VI. Fig. 4) is, as the other part of the test, closely set with small tubercles. 

 The genital openings are rather large, the ocular plates are widely separated from the periproct, 

 which is covered by smaller plates rather regularly arranged. 



') The figures (PI. VI. Figs. 8, 9, n) do not show this feature clearly. 



