58 ECHINOIDEA. I. 



much those of Ech. tenue, and almost still more those of Ph. placenta. The widenings from the 

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

 rather often quite down at the side as in Pit. placenta. In the triphyllous pedicellarise (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 genus Echinosoma. 



In the description of tPkofmesoma* iiranus (loc. cit) Agassiz uses the expression the 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 Ph. uranusf? On this basis st. 78 is named without any reservation as a 

 locality of /%. uranus (comp. Calveria gracilis and Echinosoma tenue\ 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 Phormosoma uranus (without any interrogation), as has been done by Agassiz (Chall. Ech. 

 PL XVIII. c. Fig. 12). 



The description of /%. uranus given here does not at all agree with the excellent description 

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

 is no Ph. uranus 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 a 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 Ph. uranus, there is but little difference between the spines of the actinal 

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

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

 Peter sii to be synonymous with Ph. uranus. Although the form he called Ph. Petersii, differed very 

 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. uranus and the Blake-specimens of 

 Ph. Petersii, 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 PA. uranus*, 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 /%. 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 Ph. Pelersii 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 



