ECHINOIDEA. I. 



12. Only every other interambulacral plate above the ambitus 

 with a primary tubercle; the primary spines rather short, 



greenish; the form of the test almost globular Echinus ntr.lo Lamk. 



Only a few interambulacral plates nearest to the apical 

 area want primary tubercle; the primary spines most fre- 

 quently rather long, reddish; the test high or more or less flat Echinus acutus 1 ) Lamk. 



13. The spicules branched in the ends, none dumb-bell-shaped; 

 the globiferous pedicellarise with long, muscular neck; no 



glands on the stalk. The pores multigeminate Strongyloccntrotus drebachiensis (Mull.) 



The spicules of the pedicellarise dumb-bell-shaped, those 

 of the tube feet branched in the ends; the globiferous 

 pedicellarise without neck, with glands on the stalk. The 

 pores multigeminate Sphcerechinus granuiaris*) (Lamk.). 



Several results of importance to the study of the geographical distribution will appear from 

 the present researches. A complete representation of these results must, however, be delayed, till the 

 irregular Echinids have been treated. Here I shall only briefly mention one feature of greater interest, 

 viz. the resemblance between the arctic-subarctic and the antarctic-subantarctic Echinid-fauna, as this 

 resemblance is chiefly based on the regular Echinids. 



Meissner (285) gives a comparison of the Echinid-fauna of the two regions after the state- 

 ments in the literature: one species occurs in both these regions, is < bipolar*, viz. Echinus norvegicus. 

 The following species represent each other: Cidaris canaliculata and papillata, Echinus magcllanicus 

 and miliaris, E. margantaccus and clcgans, Strongylocentrottis albus and drebachicnsis, Schizaster Phi- 

 lippii and fragilis. I shall express no opinion with regard to the two Schizaster-species , but all the 

 other points of resemblance between the two faunas are quite illusory. I have shown above that 

 Echinus norvegicus is not bipolar. The statement originates from Agassiz (Challenger Echinoidea 

 p. 117), but is wrong. The specimens (from st. 308) that have been referred to Ech. norvegicus, are 

 partly Sterechinus magcllanicus, partly an Echinus-species that has nothing to do with norvegicus; it 

 belongs to the species with primary tubercle on all the ambulacral plates; it is perhaps a new species. 

 ( 'it/firisi> canaliculata and papillata can in no way be said to correspond to each other, they belong 

 to two different genera, Stercocidaris and Dorocidaris\ any two other Cidarids might as justly be said 

 to represent each other. Echinus* magellanicus and miliaris, to be sure, are rather similar with 

 regard to habitus, but as they belong, not only to two different genera, but to two different sub- 



') With regard to var. tnedilerranea, Flemingii, and norvegicus I must refer to the description above (pp. 154155). 

 2 ) I cannot give the characters of Spharechinus roseus more particularly, as I have not seen this species; the reader 

 is referred to Russo's description of it (347). 



