41 



pedina, Stomechinus, Micropedina, Heterocidaris, Polycyphus and Codecliinus. IV. Sub- 

 fam. Orthopsinæ, comprising no recent form, iiut tlie fossil genera Orthopsis, Eodia- 

 dema, Peronia, Echinopsis and Gymnodiadema. — This classification has been adopted 

 with a little modification by Gregory in the „Treatise on Zoology", ed. by 

 Ray Lankester (Part III. Echinoderma. 1900). Lastly Lambert ') arranges the recent 

 and fossil genera of Diadematids in the auMam. Diadeniince, with the Tribus: Astra- 

 pygince and Aspidodiademince , subfam. Tiarinœ, with the Tribus: Hemicidarinœ, 

 Eodiademinœ, Pseiidoscdeninœ, Pseiidodiademinœ, Diplopodinœ and Glyphocyphinœ; 

 subfam. Pedininœ, with the Tribus: Orthopsinæ and Climapedimv . Lambert's classi- 

 fication is „évidemment encore artificielle el elle conserve l'inconvénient de separer 

 d'une facon trop absolue des genres que rapprochent une partie de leurs caractères" 

 (Note sur quelques Éch. éoc. de l'Aude p. 512) and as he names only a few of the 

 genera of his dilTerent tribus it is rather difficult to get a quite clear understanding 

 thereof. Duncan's attempt at giving a natural arrangement of the recent and fossil 

 genera seems to nie the more important; in any case it is very radical and con- 

 sistent. However, I cannot adopt his classification. To be sure my knowledge of 

 the fossil Echinids is rather small and exclusively based on literary studies; but 

 trusting to my researches on the recent forms I think it not loo bold to draw 

 some conclusions also as regards the fossil forms. Now there cannot be the least 

 doubt that Duncans classification is quite unnatural as regards the recent Diadema- 

 tids, and so it is probably not better for the fossil ones. Thus Lambert, whose 

 knowledge of the fossil forms is so very profound and extensive, says of this 

 classification that it presents „une inégalité et une confusion regrettables, car les 

 genres successivement énumérés n'ont souvent entre eux que des rapports très 

 éloignés. Ainsi on y voit figurer comme sous-genre d' Acrocidaris polypore, à tuber- 

 cules crénelés et perforés, un Arbacien, Acropeltis, oligopore, à tubercules lisses et 

 imperforés. Diplopodia à tubercules crénelés, Pedinopsis à tubercules lisses, Acanth- 

 echinus pourvu de fossettes et Phimechinus polypore, à tubercules imperforés, s'y 

 succèdent" (Éch. éoc. de l'Aude, p. 513). 



Duncan considers the structure of the ambulacra as being of primary taxo- 

 nomic importance, whereas the „very popular and useful" arrangement of the 

 genera by the existence or not of crenulation and perforation of the primary 

 tubercles is loo artificial, „for the physiological importance of the superficial struc- 

 tures is exceedingly small". — „It may be stated as a general truth, that if these 

 genera be classified by the ornamentation of the tubercles, groups possessing-¥ery 

 diverse ambulacra will be associated". — 1 have already in the Ingolf-Echinoidea I. 

 (p. 12^ — 13) on treating the classification of the Cidaridæ criticized Duncan's opinion, thai 

 structures „of no physiological importance" cannot be used as systematic characters. 



') Note sur quelques Échinides Eocenes de l'Aude (Bull. Soc. Géol. d. Fr. 3. Sér. XXV. 1897) and: 

 Étude sur quelques Échinides de l'Infra-Lias et du Lias (Bull.. Soc. de l'Yonne. ISH9). 



I). K. I). N'iclensU. Sflsk. Ski-., 7. li:iliUi_'. nnturviilcnsk. l>^ iiiiitliom. Alil, 1. 1. 



6 



