ECHINOIDEA. I. 57 



Agassiz (p. 96) mentions the pedicellariae as long stemmed with a small head articulating with a 

 second stem, from twice to three times the length of the head . This sounds very mysterious, and 

 the figure, to which reference is made (PI. XYIII. a. Fig. II), gives no clear information — the pedi- 

 cellaria figured there seems to be a quite common well-made one. May not this second stem» 

 possibly be the neck? A second kind of pedicellaria with an inverted conical head, and a compara- 

 tively stouter joint articulating upon a long stem is seen from the figure to be, in spite of this 

 remarkable description, a quite common triphyllous pedicellaria. Still a third kind of pedicellaria; 

 with a shorter articulation and a large head is mentioned; to judge from the figure it must be the 

 same kind as the one with the remarkable second stem , and they seem both of them to be the 

 smaller form of tridentate pedicellariae. To be sure, the similarity is not striking, and it may also be 

 possible that they belong to a quite different species, which has wrongly been referred to Ph. tenue. 

 The large form of tridentate pedicellariae is not at all mentioned in the description. — The longitudinal 

 muscles are well-developed, organs af Stewart seem not to be found. By its spines, pedicellaria;, and 

 the structure of the test (the actinal side only little different from the abactinal side) this species is 

 distinctly distinguished from the genus Phormosoma. It must form a separate genus, and must get 

 the name oiEchiuosoma proposed by Pom el (324) for this species and Ph. it ran its, although this name 

 is not especially significant for these species the test of which is so very soft and thin, and which are 

 only provided with uncommonly few spines. 



Of the Echinothurids referred by Agassi z to Ph. tenue I have examined a specimen from 

 Chall. st. 272. It proved to belong to a quite different genus together with Ph. Asterias A. Ag., under 

 which species it will be more nearly mentioned. On the label was found a point of interrogation, but 

 of this doubt nothing is said in the text, and st. 272 is given without any reservation as a locality 

 of Ph. tenue. 



The above mentioned specimen from Chall. st. 184, which is by Agassiz referred to Asthow- 

 soma gracilis, is no doubt very nearly allied to Echinosoma tonic. Of the large form of pedicellariae 

 I have, unfortunately, only seen one broken specimen, by which it was not to be decided with certainty 

 whether the apophysis continues into the blade as a crest. The smaller form of pedicellariae is very 

 similar to those of Ech. tenue; the triphyllous pedicellariae are a little narrower than in this species, 

 but agree with it in the development of the cover-plate. Also the spicules are a little narrower than 

 in Ech. tonic; no sucking disk; the tube feet in one almost regular series. There can scarcely be 

 any doubt that it is a species of the genus Echinosoma, and, moreover, a new species. As I can give 

 no sufficient description of it, I shall give 110 name to it. 



Phormosoma uranus Wyv. Thomson is, no doubt, most nearly allied to Ech. tonic, as also 

 observed by Agassiz (Chall. Ech. p. 103). Only 3—4 large primary spines are found in each side of 

 the ambulacral and interambulacral areas on the actinal side at the ambitus, otherwise only scattered 

 small spines. All the primary spines are broken on the type specimen of Wyv. Thomson, but no 

 doubt they are provided with a little hoof in the point as in Ech. tonic. The tube feet 011 the actinal 



side are arranged almost in one series 



, only a few outside of it. Of the tridentate pedicellariae 



I have only found the smaller form (PI. XU. Fig. 36). (The head up to i mm ); they resemble very 



The Ingolf-Expedition. IV. i. S 



