SOME WEST INDIAN ECHINOIDS. 21 



zu begrunden, mochte ich nicht emphfehlen."" It must be agreed that the only- 

 difference from the genus Arseosoma pointed out in the Zngro?/ Echinoidea is that of 

 the pediceHarit?; thougli conspicuous enougli, tliis difference is certainly not very 

 fundamental, and in case no other structural diU'crences could be found, it wouUl per- 

 haps not really be wortli while to maintain the group of species hystrix and gracilis, 

 as a separate genus. But there is a difference in the test-structure, which, together 

 with the characters derived from the pedicellaria?, seems to me to make it fully 

 justifiable to maintain liysirix as the type of a separate genus, namely, that the 

 membranous spaces between the plates are much less developed than in all the 

 species referred to Arxosorna (compare Plate 13). That this fact also holds good 

 for the species gracilis is shown by figure 4 on Plate 17a of the Challenger Echi- 

 noidea, and it is also especially pointed out in the description (p. 90). Accordingly 

 I think the genus valid. 



Regarding the name of this genus, Galveria, I am not going to change it at 

 present. In a recently published paper: On some Points in the Nomenclature of 

 Echinoids (Ann. Mag. Nat. Hist., ser. 8, vol. 5, 1910, p. 117) I have made the pro- 

 posal that some of the more important echinoid and other names should be inter- 

 nationally protected, as exceptions from the priority rule. I think this is another 

 case where an exception should be made. It is evident that the first application 

 of the name Oalveria hystrix (to the starfish Koreihrastcr hispidus) was due to a 

 mistake and it is not even accompanied by any description, so that It can only 

 indirectly be seen that it is the starfish named above which is meant. It is then 

 only just that the name Galveria hystrix be kept for the species described so excel- 

 lently under that name by Sir Wyville Thomson. 



On seeking for possible characters for generic differentiation between hystrix 

 and fenestratum, I examined their internal anatomy, without finding any differences 

 of importance. Especially is it to be noticed that the Stewart's organs are large in 

 both, and of the same shape as in Sperosoma grimaldii, so admirably illustrated 

 by Professor Koshler.'' On examining these organs in a specimen of fenestratum 

 I was very puzzled to find them only in two radii; a closer examination, however, 

 revealed the remarkable fact that those of the three other radii were lying in the 

 dental pvramid, within the alveoli. How they had actjuired this remarkable 

 position "seems difficult to understand; but the fact that tliey were turned inside 

 out seems to indicate that it must be due to an inversion which has taken place 

 in an early stage of their development. The alternative that it might possibly be 

 due to hard pressure on the test of the animal during its passage from the sea 

 bottom to the ship's deck among the other material contained in the dredge 

 seems excluded by the facts of the inversion of the long organs, and that the deli- 

 cate walls of the dental pyramid are intact. 



DIADEMA ANTILLARUM Philippi. 



In his Revision of the Echini, Mr. Agassiz distinguished only two species of 

 the genus Diadema: D. mexicanum and D. setosum. In the latter were included as 



a Echinoiden der Deutschen Tiefsee-Expedition, p. 120. 



b Resultats des Campagnes scientifiques de S. A. S. le Prince de Monaco. Fasc. XII. Echinides 

 et Ophiuros * * * de V Hirondelle, 1S98, pi. 4, fig. 8. 



