ECHINOIDEA. I. 177 



Hygrosoma, the difference between the latter and the genus Tromikosoma becomes rather more slight 

 than stated in the diagnoses. Then there is only any difference of importance in the form of the tri- 

 dentate pedieellariar, bnt this difference is so great, that I, at all events for the present (until transi- 

 tional forms become known), must regard the genus Tromikosoma as a legitimate one. 



Kamptosoma asterias (p. 60). All the three specimens from Chall. st. 272 which Agassi/, has 

 determined as Phormosoma tonic/, are A", asterias. After a renewed examination I must regard it as 

 unjustified to establish a separate species of this genus on them. - It is the primary spines on the 

 actinal side that are flat and widened at the point (PI. XIV. Fig. 29); below they are round, tubular, 

 and then they become evenly flattened towards the point. They are a little curved; a hoof is scarcely 

 found. The spines nearest to the mouth are surrounded by a rather thick bag of skin, not widened 

 at the point. The small, accessory ambnlacral plates are really wanting-, only nearest to the peri- 

 stome a sing-le one may be found. For each ambnlacral plate here are as usual three branches from 

 the radial canals, but two of them are quite thin and their ampulla; rudimentary, and their tube feet 

 are not developed at all. 



Sperosoma Grimaldii (p. 75). Of this species I have found ca. 20 specimens in the museum of 

 Paris ( Talisman , the Azores, Morocco, 300 — 1257 m.), determined partly as Phormosoma uranus, partly 

 as Astkenosoma hystrix. Our museum has further received some specimens of different sizes from the 

 Faroe Channel (59° 29' X. L. 7 51' W. L. 580 — 689 fathoms. Michael Sars . Ad. S. Jensen), a corrobora- 

 tion of the supposition with regard to its geographical distribution expressed above. - Rather great 

 variation proves to be found in the mutual relation of the size of the abactiual ambnlacral plates; 

 accordingly there cannot be laid much stress on the deviations in this respect from the type specimen 

 of Koehler described above, and there can be no doubt that the large specimen figured on PI. IV. 

 Fig. 3, is a real Sp. Grimaldii. 



Prionechinus sagittigcr (p. 84). As far as can be seen on the type specimen preserved in 

 alcohol (st. 218), no grooves are found in the test; to be able to state this fact with certainty, it will, 

 however, be necessary to examine a dried specimen. 



Ecliiiuis luctdus (pp. 100, 105) has calcareous plates in the buccal membrane as the other genuine 

 Echinus-species ; they are simple fenestrated plates as in Ech. Alexandri. There are no spines on the 

 buccal plates (p. 161, note). 



Stereckinus margaritaceus (pp. 101 — 102). De Loriol has called my attention to the fact that the 

 figures of Ech. margaritaceus given in Voyage de la Fregate Venus . Zoophytes PI. VI. 1, do not 

 agree with Koehler's description of St. antarcticus, especially as all the ocular plates in margaritaceus 

 are shut off from the periproct. Trusting to the interpretation by Agassiz of Ech. margaritaceus as 

 the correct one, I had omitted to examine this question more closely. According to a kind informa- 

 tion from Dr. Gravier the type specimen is no more found in Pans. But to judge by the figures in 

 Voyage de Venus there can scarcely be any doubt that Agassiz's (and my) interpretation of Ech. 

 margaritaceus is incorrect; besides the ocular plates being shut off from the periproct, it seems also to 

 appear from these figures that there is a primary tubercle on all the ambulacral plates. But then I 

 do not see how St. magellanicus is to be distinguished from margaritaceus, and it is an obvious sup- 

 position that they are reallv one species; if this be the case the name of magellanicus will only be a 



The Ingolf-Expedition. IV. I. 23 



