^8 ECHINOIDEA. I. 



Sars has it from 50 — 100 fathoras; tlie specimens taken by Dr. H. I. Hansen at Svracnse are from 

 20—30 fathoms. The form mentioned from Florida is stated by Rathbnn (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, II, 16, 19—21, 23, 26, 28, 30, 36. PI. XI. Figs. 12, 16, 17, 23, 28, 30, 32, 33. 



■ PI. XVI. Fig. I. 



Diaiii. of the peristoine Diam. of the apical area Longest spines 



14 mm. 15 mm. 



12 — 13 — 65 mm. 



10-5— 10-5— 48 — 



10 — 13 — 62 — 



9 - 12-5— 47 - 



9 - 13 - 50 - 



6-5- 8 - 50 - 



4 — 5 — 26 ~ 



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

 the fonn 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 jDerpendicular, below slightly 

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

 two lowermost interambulacral piates are situated almost horizontally. 



The interambulacral areas are 3^2—4 times as broad as the arabulacral areas; the\- consist of 

 5 — 7 piates. The areoles are deep, the edge round them raised, with a single circle of 15 — 16 more 

 conspicuous tubercles; in large .specimens these are more indistinct. The other part of the piates 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 piates join, a narrow naked stripe is scarcely seen, in the largest specimeu not at all. 

 The i^lates 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 10—12 ambulacral piates for each interambulacral jslate. 

 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 Httle smaller. (In D. papillata and C. a/finis the 

 pores are of equal size; in the latter there is a rather broad partition-wall between them)'). 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 piates are only seen with difficulty (PI. VI. Fig. 11). 



The piates of the peristome are set with numerous small tubercles, but only 011 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 piates are widely separated from the periiiroct, 

 which is covered by smaller piates rather regularh- arranged. 



J) The figures (PI. VI. Figs. 8, 9, 11) do not show this feature clearly. 



