ECHINOIDEA. II. 



89 



tinderstand tlie true relatioiisliip not only of many aberrant ;^roups of Spatangoids, but also tlieir 

 relationship to the Chpeastroids and Echinolanipacke . ( Chall. -Kch. p. 148). 



I si^'e here a graphic representation of the mutual relationshi]) of the .Si)atang-oid.s, as I under- 

 stand it. It will be seen that my view of the Mrridostcniata is in rather close accordance with that 

 represented in the tabular view of the Meridostcnii <;iven 1)\- Lambert.' I ma\- notice ex])ressly that 

 it is not meant as a genealogical tree of the genera. As for the families, I tlo not doubt that the\' 

 have realh' been derived from one another in the direction here indicated. 



Plexechinus 

 Cystecliiuus(?)^ 

 Pilematechinus 

 Urechiuus 



Pourtalesia Echinosigra 



Spatagocystis Ceratoph)sa 



Cystocrepis Helgocystis 



Echinocrepis 



Calymnid;e Sternopatagus 



Oy Stereoj-jneustes 



Ananchytidse 



Collvritidse , 



Clypeastroidea 



1-1 

 o 



r-h 

 O 



tn 



Holectypoidea 





Spatangidcc3 

 Pakeostomatidu; 

 Palseopneustidae 

 Aeropidie 



Cassidnloidea 



Diadeniina 



1 Etudes inorph. snr le plastron des Spatan<(ide.s. As for Lambert's remark (Op. cit. ]>. 9;,) that the Pourtalesia; 

 must form a small separate family -reliee par Urechiuus aux vrais Annnchytitice et rattachee aux S/>n/ntii;i(f(F ])ar Piila-otiopus 

 et Physnster .^ I must refer to the above remarks agaiust seeking transitions between the I'ourtalesiie and the Atnpliisternata. 

 Lambert is here, evidently, in disaccord with the views otherwise expressed throughout that excellent paper. 



-' This genus is quite insufficiently known and possibly does not really belong to this family. (Conip. abovep. 46, 49). 



3 Sensu latiori, comprising Spa/ni/i;iua, Rrisshm etc. 



The Ingolf-Expedition. IV. :;. j2 



