58 ECHINOIDEA. I. 



much those of Ech. tenue, and ahiiost still more those of P/i. 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 P/i. 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 iPhormosomay uramis (loc. cit.) Agassiz uses the expression the onl\- 

 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. jiranus?'? On this basis st. 78 is named without any reservation as a 

 locality of </%.» -uranits (comp. Calvcria gracilis and Echinosoma tcinic). 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 tinder the 

 name of PJiormosoma u?-anns (without any interrogation), as has been done by Agassiz (Chall. Ech. 

 PI. XVIII. c. Fig. 12). 



The description oi ^ Ph.> nran7(s 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. lira mis at all. As I have examined the tyjje specimen of W>"v. 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 Phorniosonia Pclcrsii., and describes it as <.a species with an extremeh' 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. icranus, there is but little difference between the spines of the actinal 

 and abactiual surfaces. The coronal plates of this species are more namerous than in any other species 

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

 Petersii to be synonymous with Pli. uranus. Although the form he called Ph. Peter sii., (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 tyjie specimen of Ph. nraniis and the v Blake -specimens of 

 Ph. Petersii^ that <- the differences which had been noticed between them were nierel\- 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 siJecimen of this Ph. ^iranusiy., which he has got from the Smithsonian 

 Institution (from ( Albatross>), and l)y which lie has determined his specimens as Ph. nrainis. Our 

 museum has also from Smithsonian Institution received a specimen of this «/%. uranusi., 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. 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 ma\- have been broken in the speci- 

 mens of Agassiz, and in this case there is reall\- not much ilifference to be seen between the spines 



