Miscellaneous. 231 



them at leisure, to complete the diagnosis of the genus and determine 

 the place which this curious typo shoiild occupy in the series. 



Before the Exhihition of 1SG7, only a single specimen of Astero- 

 stoma, from Lamarck's oolloction, was known. In 1847 MM. Agassiz 

 and Desor, in the ' Catalogue raisonne des Echinides,' had made of 

 this imique specimen the type of the genus Asterostoma, and given 

 the species the name of e.vcentncum. Although noticing that this 

 genus approaches Echinocorys (AnancJu/tes, Lamk.) and that the 

 anterior ambulacral area is formed of smaller pores than the paired 

 ambulacral areas, MM. Agassiz and Desor place the genus Astero- 

 stoma at the end of the family Cassidulidse, not far from ConocIi/pei(S. 

 In 1865 D'Orbigny described the genus Asterostoma and the only 

 species which it then contained. Because the anterior ambulacral 

 area differed from the others, not only in its form but also in the 

 structure of its pores, the author of the * Paleontologie Franfjaise,' 

 justly considering this organic character very important, thought that 

 the genus must be placed among the Spatangidae, in which, as is 

 well known, the anterior ambulacral area is never like the others. 



Some years later, M. Desor, in the ' Synopsis des Echinides fossiles,' 

 had again to turn his attention to Asterostoma. That eminent natura- 

 list discusses and combats the opinion of D'Orbigny : the position of 

 the peristome, which is almost central in Asterostoma, the strongly 

 marked furrows which surround it, and of which no trace exists in the 

 true Spatangidae, and the structure of the apical apparatus, w^hich, 

 from the impression left at the apex of the ambulacral areas, appeared 

 to affect an elongated form, led M. Desor to remove the genus As- 

 terostoma from the Spatangidae ; and it appeared to him much more 

 natural to unite it with the Galeritidae, near DesoreUa and Pacliy- 

 clypeus, which, as he says, combine with a central and angular 

 peristome an elongated apical apparatus. 



The two new species of Asterostoma which I have just studied, 

 from the fine preservation of some of their essential organs (the 

 paired and anterior ambulacral areas, the peristome, the apical ap- 

 paratus, &c.), whilst enabling me to complete the diagnosis of the 

 genus, leave me in no doubt as to the place which it should occupy ; 

 and I have no hesitation in ranging it in the family of the Echiuo- 

 corydeae, between Stenonia and Holaster. That important character 

 upon which D'Orbigny dwelt, namely the diff'erenco of structure 

 between the anterior ambulacral area and the others, is still more 

 apparent and marked in our two new species. It is not only the 

 ambulacral pores that are smaller and otherwise arranged in the 

 anterior ambulacral area ; the poriferous plates themselves are higher 

 and consequently much less numerous; and this clearly marked dif- 

 ference gives to the upper surface a physiognomy which is certaiidy 

 not that of the Echiiiobrissidaj and Echinoconida3. M. Desor, to 

 support his opinion, especially invoked the almost central position of 

 the peristome and the deep furrows which converge into it. In the 

 new Asterostomas from Cuba, the peristome is much more excentric 

 in front, the ambulacral furrows which surround it, although still 



