140 ECHINOIDEA. I. 



Colobocentrotus Brandt (emend.). 



Pores mnltigeminate; primary tubercle on all the ambulacral plates. The pore areas on the 

 actinal side petaloid. The buccal membrane with numerous fenestrated plates, partly hidden in 

 the skin. Spines both on the buccal plates, and on some of the plates outside of these. The test 

 oblong, flat. The spines very short, thick, truncate, form a dense mosaic on the abactinal side. The 

 spines on the ambitus longer, flat; those on the actinal side of the common form. 

 Species: C. atratus (L.), Mertcnsii Brandt. 

 Distribution: The Indo- Pacific Ocean. Littoral forms. 



IncertcB sedis: 



Echinus multicolor Yoshiwara. 

 Toxopneustes maculahis (Lamk.). 

 Strongyloccntrotus mexicanus (Ag.). 

 nudus (Ag.). 

 globulos^ls (Ag.). 



The system given here is, I think, in all essentials an expression of the natural relation of 

 these forms. To be sure, we must a priori hesitate before building up a system chiefly on so minute 

 things as pedicellariae and spicules. But the result is the best possible one: no undoubtedly connected 

 forms are separated ; on the other hand, forms hitherto placed very far from each other in spite of their 

 great similarity as to habitus, are now put together (Parcchinus and Loxechinus). That the boundary 

 line in one place is somewhat arbitrary is no important objection to the system - - this will be the 

 fact everywhere, where transitional forms are found. The genus Pscudechinus is here referred to the 

 Echmometridce; but there can scarcely be any doubt that it is also closely allied to the Echinidce, it 

 seems especiallyto be a near relation of Sterechinus magellanicus. Here it has been referred to the Ecliino- 

 metrida- especially for practical reasons, it being then possible to give a quite certain character of 

 these two families: in one teeth on either side of the blade of the globiferous pedicellariae, in the 

 other only one unpaired lateral tooth. Pscudechinus forms the connecting link between the two 

 families, and it is especially worthy of notice that in this genus may sometimes be found an indication 

 of a lateral tooth also on the other side of the blade of the globiferous pedicellariae. 



The family Toxopneustid<z is sharply limited from the other two families, without transitional 

 forms. Objections can scarcely be raised against the subfamily Schizechinina - all the genera 

 referred thither, are evidently closely allied. Less sure are the subfamilies Parasalenince. and Strongy- 

 locentrotmee. Possibly the feature whether the globiferous pedicellariae have a neck or not, is not of 

 so great importance, as has here been supposed; but I think it impossible to decide this fact with 

 certainty, as long as only so few forms belonging here are known. 



That no other outer characters are found in these forms, which may be used in the classifica- 

 tion, I think to be certain; both the test and the spines have been studied rather thoroughly, so that 

 anything new of importance is scarcely to be expected here. It is hardly probable that the inner 

 anatomical structure will yield systematic characters of any greater importance, but this question, at 



