ECHINOIDEA. II. 41 



actinal side, only a little shorter and clad with a thicker skin. The spines npon and around the peri- 

 stome are somewhat dubshaped (PI. IX. Fig. 39); the base of the primary spines is rather large; it 

 seems somewhat exaggerated in the Chall. -Ech. PI. XXX. Pig. 20 — the Fig. 21 of the same plate, 

 representing a miliary spine, according to the explanation of the plate, it is better not to speak of. 



In the specimen of y^""" the primary tubercles fonn, on tlie abactinal side, an ahnost regular 

 vertical series in each row of piates, the tnbercles being placed in the middle of the piates. In later 

 stages other tubercles grow larger than the primar\- - ones, thns obscnring the vertical arrangement, 

 and it even sometimes looks as if the true primar\- tubercles ha\e become resorbed'. 



In grown specimens the arrangement of the large tubercles is quite irregular, as described by 

 Agassiz. In the : Challenger -Ech. p. 147 Agassiz remarks that in some specimens there may be 

 rudimentarj- bourrelets. I have seen the same thing. The Figures 10 and 11, PL VI represent the 

 actinal side of two specimens, one with a very distinct bourrelet, the other with scarceh' a trace of it. 

 Also in f '. gigantens this feature is found (Panamic Deep-Sea Ech. p. 155) though not so distinctly 

 developed, judging from the figure (PI. 73. i) to which reference is made. 



The tube-feet ma\- be quite devoid of spicules, or with a single series of simple, somewhat spinous 

 rods with rounded ends (PI. IX. Fig. 8) in the actinal, penicillate tube-feet as well as in the simple 

 abactinal feet; in the lower part of the tube-foot they are generally more irregular, more or less 

 branched. The peculiar fenestrate rods of the filaments have been figured b>- Loven (On Pourtalesia. 

 PI. VIII. ^6); the>- are, however, less fenestrate than shown there. No supporting skeletal piates are 

 found below the rods of the filaments in the actinal tube-feet. The frontal tube-feet are simple, without 

 a sucking disc (rosette), not differing from those of the other ambulacra. No large, specially de\eloped 

 subanal tube-feet. 



Two sorts of pedicellariæ are figured by Agassiz (« Challenger -Ech. PI. XXX. 22—24), '^i^- 

 tridentate (flarge trifid longstemmed pedicellariæ*) and ophicephalous («shorter roundheaded pedi- 

 cellariæ , in the e.xplanation of the piates cailed clubshaped pedicellariæ with heavy-stemmed articula- 

 tion |. I find five different kinds of pedicellariæ in this species, viz. globiferous, tridentate (two sorts), 

 triplnllous and ophicephalous pedicellariæ. 



The globiferous pedicellariæ (PL IX. Fig. 35) have a rather conspicuous cap of evidenth' glan- 

 dular skin, thickening especialh- over the point of the vahes. The latter (PL IX. Fig. 9) are very char- 

 acteristic; the blade is a closed tube ending in a large opening surrounded usually by nine long, 

 slender gracefuUy cur\ed teeth, one of which is median in the onter edge. The basal part is large, 

 rounded; no neck. The stalk consists of long, thin calcareous fibres, connected only above and below; 



■ Agass iz (Panamic Deep-Sea Ecli. p. 153, 159-60, 166) has found such resorption to occur in Urecltinus gigantens 

 and Cystechinus, as also iu Pælæopnensles and Lhwpneustes; he sees thereiu a proof of <.the constaut struggle that must exist 

 for the deposition of needed carbonate of hme ... The least disorder in the growing tissue of any part of the test evidently 

 affecting at once the active deposition of the carbonate of Ume of that region». I may, however, remark that the tubercles 

 of these forms are ven,- easily broken off. It is quite easy, as I have tried myself, in this way to produce all the different 

 stages of .resorption, figured by Professor Agassiz (especially PI. 86. 2). The suggestion therefore does not seera unreason- 

 able that at least part of what Professor Agassiz thinks to be the result of a resorption is, indeed, only the result of the 

 animals having been tbadly rubbed« in the dredge or otherwise. That the empty place of such a primarj- tubercle may be 

 covered by a pigmented skin (as I have seen it very distinctly in a specimen of Pourtalesia Jeffreysi) is no proof of a res- 

 orption having occurred; it may as well be the result of some injury, by which the spine and tubercle was lost some 

 time before. 



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