Miscellaneous. 2'M 



tliom (it leisure, to complete the diagnosis of the genus nnfl (Icitcrmine 

 the place wliicli this curiitus type should occupy in the series. 



Ik't'ore Ihe Kxhihition of lHf!7, oidy a siu^^de spocinicn of Astero- 

 stoinn, from I^amarck's collection, was known. In 1 H47 MM. Ag.'issiz 

 and JJesor, in the ' Cataloj!;ue raisonne des Efthinide.s,' had made of 

 this unique specimen the type of the genus Astfrostoma, and given 

 the species the name of excentricum. Although noticing that this 

 genus approaches Evhinocorys (Ananchi/tes, Lamk.) and that the 

 anterior amhulacral area is formed of smaller pores than the paired 

 amhulacral areas, Mif. Agassiz and Desor jjlace the genus Astero- 

 stoiiui at the end of the family Cassidulida;, not far from Conochipeus. 

 In 1805 D'Orhigny described the genus Asterostoma and the only 

 species which it then contained, lieeause the anterior amhulacral 

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

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

 justly considering this organic character very important, thought that 

 the genus must be placed among the Spatangida;, in which, as is 

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



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

 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 furro%\s which surround it, and of which no trace exists in the 

 true Spatangidaj, and the structure of the apical apparatus, which, 

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

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

 terostonui from the Spatangida) ; and it appeared to him much more 

 natural to unite it with the Galeritidoc, near Desorella and Fachy- 

 dypeus, 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 amhulacral areas, the peristome, the apical ap- 

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

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

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

 corydese, between Stenonia and Holaster. That important character 

 upon which D'Orbigny dwelt, namely the difference of stnicture 

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

 aj)parent and marked in our two new species. It is not only the 

 amhulacral pores that are smaller and otherwise arranged in the 

 anterior amhulacral 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 certainly 

 not that of the Echiiiobrissidaj and Echinoconida;. M. Desor, to 

 support his opinion, especially invoked the almost central position of 

 the peristome and the deej) furrows which converge into it. In the 

 new Asterostomas from Cuba, the peristome is much more excentric 

 in front, the aml)ulacral furrows which surround it, although still 



