94 



allowed to examine this most interesting form , which is described below as Op- 

 echinus spectubilis n. sp. Thus we know now two living representatives of this very 

 remarkable group. 



Opechinus variabilis (Döderl.). To the description of this species may be 

 added some few remarks. The spines are smooth, not swollen at the point, ending 

 in a centra] thorn with a circle of small thorns at its base. The globiferous pedi- 

 cellariæ (PI. VI. Fig. 27. PI. VII. Fig. 2) have no lateral teeth; the outer corners of 

 the basal part are marked and more or less produced; the blade is (juite open or with 

 a single transverse beam. The ophicephalous and triphyllous pedicellariæ (PI. VII. 

 Fig. 7, 49) do not present any remarkable characters. Slender bihamate spicules are 

 found in the tubefeet and in the head of the globiferous pedicellariæ. De Meijere 

 („Siboga"-Echinoidea. p. 79) mentions some specimens of „P/eurechi/ius" variabilis. 

 Since he has sent me these specimens together with all his specimens of „Pleurecliiniis 

 bothryoides" , I can state that those (two) from St. 98 are quite different from O. 

 variabilis. They evidently belong to an undescribed species of the genus Genocidaris. 

 The specimen from St. 105 is a true Opechinus and probablj' 0. variabilis, though 

 it has comparatively fewer tubercles than the type-specimen. 



Opechinus spectabilis n. sp. (PI. I. Fig. 15). The test is low, the abactinal side 

 somewhat conical, the actinal side flat. (Diameter 30 mm., height 16 mm.) The 

 primary tubercles are noncrenulate, of about equal size in both areas, diminishing 

 a little in size towards the apical system. In the ambulacra the secondary tubercles 

 form a distinct vertical series inside the primary series. Numerous small tubercles 

 are scattered irregularly on the plates inside and above the primary tubercle, which 

 is placed close to the pores. Along the median line there is a smooth space. Be- 

 sides the depression at the median end of the suture there is, at the ambitus, an- 

 other smaller, • intermediate depression opposite to the space between the primary 

 and the large secondary tubercle. This intermediate depression appears at about 

 the 6* plate from above; below the ambitus both depressions soon disappear. The 

 pores are disposed in an almost straight series close to the edge of the area; the 

 interporiferous zone is much broader than the poriferous. The ambulacral plates 

 are a little lower than the interambulacral ones, their number being 19 against 

 16 — 17 interambulacral plates. 



In the interambulacra the secondary tubercles form at the ambitus two 

 vertical series inside and one outside the primary tubercles, almost as large as the 

 primary ones. Below the ambitus the innermost series first disappears, the two 

 other series being distinct almost to the peristome. Both these series likewise are 

 distinct almost to the apical system, whereas the innermost series only appears at 

 the 6* — 7"» plate from above. All these tubercles likewise form a distinct hori- 

 zontal series on each plate. Small tubercles cover the rest of the plates, forming a 

 close circle around each larger tubercle. The median line is naked. At the am- 

 bitus there are no less than 6 depressions in each horizontal suture, the two angular 



