58 ECHINOIDEA. I. 



mncli those of Ech. terme ^ aiid alinost still more those of Pli. placenta. The widenings from the 

 upper eiid of the apophysis reach most frequently, to be sure, to the edge of the blade, but they end 

 rather often quite dowii at the side as in Pli. placenta. In the triphyllous pedicellariæ (PI. XII. Fig. 17) 

 the cover-plate is well developed, the edge finely serrate. There can scarcely be any doubt that also 

 this species will have to be referred to the genns Echinosoma. 



In the description of <.Phormosoinay> urmms (loc. cit.) Agassiz uses the expression tthe only 

 specimen collected;, but nevertheless puts down for it two different localities, st. 6 and st. 78. This 

 riddle I am able to solve. In British Museum a quite small Echinothurid is found from Chall. st. 78, 

 determined by Agassiz as Pli. jiranusf? On this basis st. 78 is named without any reservation as a 

 locality of <..PIi.» uranus (comp. Caiven a gracilis and Ecliinosovia femte). With regard to this specimen, 

 it is otherwise very badly preserved, and not a single pedicellaria is kept. It is quite indeterminable, 

 and consequently it cannot be considered to be correct to figure details of this specimen under the 

 name of Plion/iosoiiia uranus (without au}' interrogation), as has been done by Agassiz (Chall. Ech. 

 PI. XVIII. c. Fig. 12). 



The description oiPh./> uranus given here does not at all agree with the excellent description 

 given by Koehler (229). The incongruity arises from the faet that the species described by Koehler 

 is no Ph. urarnis at all. As I have examined the type specimen of Wyv. Thomson and also a 

 specimen of the species Koehler has had before him, I am able to express myself with absolute 

 certainty. 



In the preliminary report of the Echinids from «Blake» (6) Agassiz establishes a new species 

 under the name of Phormosoma Petersii, and describes it as ta species with an extremely thin test, 

 and one which, when alive, is greatly swollen, assuming a nearly globular outline. It is of a brilliant 

 light claret color. As in Pk. uranus^ there is but little difference between the spines of the actinal 

 and abactinal surfaces. The coronal piates of this species are more numerous than in any other species 

 of the genus.> (p. 76. op. cit). In the final report of the v Blake -Echinids (9) Agassiz states Pli. 

 Petersii to be synonymous with Ph. uranus. Although the form he called Ph. Petersii, vdiffered ver}- 

 strikingly ■:• from the specimen of Wyv. Thomson, he thinks now, after having got a specimen from 

 the Faroe-Channel of a size between the type specimen of Ph. tiramis and the vBlakes-specimens of 

 Ph. Pet er. ^11, that «the differences which had been noticed between them were merely due to age, and 

 that in this species the great development of the large primary tubercles of the actinal surface takes 

 place at a late period of growth«. 



Koehler mentions a specimen of this Ph. uramisy>, which he has got from the Smithsonian 

 Institution (from < Albatross > ) , and by which he has determined his specimens as Ph. uranus. Our 

 museum has also from Smithsonian Institution received a specimen of this Ph. uranus », which is 

 identical with the form more nearly described by Koehler. Now the question is whether this form 

 is really identical with the original PI/. Petersii of Agassiz. The expression above quoted from the 

 first note of Ph. Petersii: « there is but little difference between the spines of the actinal and abactinal 

 surfaces* does in no way agree with the species of Koehler, in which the spines of the actinal side 

 have a large, conspicuous hoof. It is possible, however, that they may have been broken in the speci- 

 mens of Agassiz, and in this case there is really not much difference to be seen between the spines 



