ECHINOIDEA. I. 



57 



Agassiz (p. 96) mentious the pedicellariæ 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 figiire, to which reference is made (PI. XVIII. a. Fig. 11), gives no clear information — the pedi- 

 cellaria fignred there seems to be a qiiite 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 pedicellariæ 

 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 pedicellariæ. To be sure, the similarit)' is not striking, and it may also be 

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

 The large form of tridentate pedicellariæ 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, pedicellariæ, and 

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

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

 the name oi Echiiwsoiiia proposed by Pomel (324) for this .species and Pli. uraiius., 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 Agassiz to Ph. temie I have examined a specimen from 

 Chall. st. 272. It proved to belong to a quite different genus together with Ph. Astcrias 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 Pli. tenue. 



The above mentioned specimen from Chall. st. 1S4, which is by Agassiz referred to Astheno- 

 soma-i gracilis^ is no doubt very nearly allied to Echiiwsoma tcnuc. Of the large form of pedicellariæ 

 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 pedicellariæ is very 

 similar to tliose of Ecli. tenue; the triphyllous pedicellariæ 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 Eck. tenue; 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 no name to it. 



■ Plioniiosoiiia , uraniis Wyv. Thomson is, no doubt, most nearh' allied to Ech. tenue, as also 

 observed by x\gassiz (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. tenue. The tube feet on the actinal 



side are arranged almost in one series 



, only a few ontside of it. Of the tridentate pedicellariæ 



I have only found the smaller form (PI. XII. Fig. 36). (The head up to i™"-); they resemble very 



The Ingolf-Expedition. I\. 1. i> 



