2Q ECHINOIDEA. II. 



fessor Agassiz remarks on this criticism: I liave stated that I thono-ht this character of no great 

 systematic importance. Dr. Mortensen is of contrar\- opinion^ (p. loi); I confess my inabihty to under- 

 stand how a statement, shown to be erroneous, can be made good again by simply reiterating it, even 

 if this is done by so eminent an authority as Profes.sor Agassiz. 



The statement that I use the spicules in the classification of the Echinothurids, after having 

 previously informed us that they are of no systematic values mtist be due to some error. So far 

 as I know I have never stated that the spicules are of no systematic value. On p. 45 I have said 

 that the spicules are almost always rather large, irregular, fenestrated plates situated more or less 

 distinctlv in 3 — 4 longitudinal series. In A. variuvi, Grubei, hctcracfis and urens they are very slightly 

 developed, onlv .small, branched calcareous pieces, rarely with a hole \ In the following lines I sa\- of 

 the sphseridife that the\- show no differences so great that they can be of any systematic importance \ 

 Perhaps it is this remark which Professor Agassiz through some lapsus has referred to the spicules. 



The difference between the genera Araosonia and Calvcria is, I agree, not so very important, 

 and since the name Calveria cannot be used, as pointed out by Professor Agassiz and most carefully 

 argued b\ Ur. P'. A. Bather", it may, perhaps, be preferable to unite C. hystrix with the genus 

 ArcBosoma; to the g&nns Asthenosojua it cannot be referred. The species A.varhim and Grubei I ha\e 

 never referred to the genus Calveria, as stated by Agassiz (p. 84). 



Professor Agassiz claims to have figured an ophicephalous pedicellaria of Phorinosoiiia lii- 

 culentiim. viz. on PI. XLIV. fig. 27 of the Challenger -Echinoidea. I may remark on this account that 

 he onl\ uRntions it in the explanation of the plates and under the name ; small short-headed, short-stemmed 

 pedicellaria ; further I lui\e by no means overlooked that figure, but mention it on p. 60 and p. 176, 

 suggesting that it ma\' represent an ophicephalous pedicellaria, but stating that I have myself been 

 unable to find any similar form of pedicellaria in this species. I think Professor Uiiderlein is right 

 in su]3posing (Op. cit. p. 121) that it does not really belong to this species. When Professor Agassiz 

 takes the peculiar modified form of tridentate (or perhaps ophicephalous) pedicellariae figured by nie 

 on PI. XIII. Fig. 16 to be the same as that which he has figured in PI. XLIV. 25—26 (« Challenger >>- 

 Echinoidea), he is quite right. I have stated that carefully on p. 60 and have given no figures of the 

 valves, finding that his figures give a good representation of the single \al\e . 



That figures of Phormosoma placenta are given in the Blake -Echini and of Plioniiusoina 

 bursariuvi in the Challenger -Echini does not eliminate the fact, that Professor Agassiz in describing 

 the latter species only points out the differences from the distantly related rPhormosotna>> luculentiim 

 but not the characters distinguishing it from the very closely related Pli. placenta. Neither are such 

 characters pointed out under Pliormosoma placenta in the Blake -Echinoidea. That there was some 

 reason for pointing out such differences appears also from the fact thai Professor Dodtrlein is now 

 inclined to regard Ph. bursarizim as only a synonym of J'/i. placenta (Op. cit. p. 127). 



Further, Professor Agassiz says (p. 85): Dr. Mortensen thinks that I am wholly mistaken in 

 suggesting an\- affinit\- between A. pellucidum and A. coriaceiuii and A. tis.s-ildfiiii/. hrca/i.';r' he has 

 suggested a new genus, Hoplosoma, for A. pellucidum, based entireh- upon the structure of the pedi- 



' The Echiiioderm iianie Calvcria hystrix. .\nn Nat. Hist. 7. Ser. XVII. J906. p. 249. 

 ' The Italics are mine. 



