120 Revieics — Wachmiuth £f Springer's Monograph on Crinoids. 



interradii of the Carboniferous family Actinocrinidge is more primitive 

 than that of the Ordovician Eeteocrinidge — a quaint paradox. On 

 the contrary the Eeteocrinid structure follows the arrangement 

 usual in primitive many-plated areas just undergoing evolution into 

 few-plated areas ; a similar arrangement is seen in JEocystis, Walcott, 

 Deutocysfis, Barrande, in Diaholocrinus of the Trenton Limestone, 

 and in the carapace of Glyptodon. The outward appearance of 

 these areas may be striking, but the structure is the reverse of 

 fundamental, and examination of the three genera refeiTed to the 

 family fails to show more important points of resemblance. It is 

 not merely simpler, but more likely to bring out affinities, if we 

 run the line between Monocyclica and Dicyclica right away through 

 the typical Camerata. We must in fact regard the two divisions as 

 exhibiting homoplastic modifications of distinct Inadunate stocks. 

 The genera are arranged in families as follows : — 



1 . Eeteocrinidse : Reteocrinus, Xenocritms, Tanaocrinus. 



2. Thysanocrinidae : Ftychocrinus, 2'hyicmocrinus, Hyptiocrinus, Idiocrinus, Lam- 



pteroc7~iniis, Sip honqcr inns. 



3. EhodocrinidEe : Ehaphanocrinus, Archceocrinus, Diaholocrinus, JRhodocriuus, 



Gilbertsocrinus, Thylacocrinus, Lyriocrinus, Anthemocrinus, 

 Rhipidocriniis, Diamenocyinus . 



4. Melocrinidse : i. Melocrinites — Glyptocrinus, Periglyptocriniis, Sfelidiocrinus, 



Mariocrinus, Scyphocrinus, Melocrinus, Ifacros/ylocrinus. 

 ii. Dolatocrinites — Technocriniis, Corymbocrinus, Patelliocrinus, Allo- 

 crinus, Centroci inus, Dotatocrinus, Stereocrinus, Sadrocrinus. 



5. Calyptocrinidse * lEucalyptocrinns, Callicrinus . 



6. Batocrinidse : i. Batocrinites — Batocrinus, Eretmocrinus, AUoprosallocj-irtns, 



Zobocrimis, Macrocrinus, Entrochocrinus, Lizygocrinus, Bar- 

 rnndeocrinus, Aorocrinits, Dorycrinws, Agaricocrinus, Acacocrinus, 

 Sabrocrinus, Desmidocrinus, Compsocrinus. 

 ii. Periechocrinites — I'eriechocrinus, Meg istocr inus, Gennceocrinus, Abaco- 

 crinus. 

 1. Actinocritiidse : Actinocrinus, Steganocrinus, Amphoracrinus, Caetoctinus, Teleio- 

 criniis, Physetocrinns, Strotocrinus. 



For practical purposes, and with the help of the keys prefixed to 

 each family, this grouping does well enough, and in the main it 

 follows the broad lines of descent. At any rate it is an improve- 

 ment on previous schemes. But it is the ill fate of such improve- 

 ments always to disclose avenues of further progress. A few such 

 may be alluded to. 



'rhe family EeteocrinidaB may be retained for Reteocrinus, but 

 Xenocrinus and Tanaocrinus are more suitably placed at the base of 

 the assemblage called Batocrinidge by our authors. 



The Thysanocrinidse, to w^hich Jaekel's Orthocrinns must now be 

 added, should be relieved of Idiocrinus. This has not a tegmeu of 

 true Camerate type; its arms, so far as known, are not pinnulate ; 

 and its dorsal cup scarcely differs from that of Anisocrinus, which is 

 a Taxocrinid. To judge from the published descriptions, it might 

 well form a family of Flexibilia Impinnata, but is a primitive genus 

 not far removed from Inadunata. It would also conduce to clearness 

 to separate Lampterocrinus and Siphonocrinus as a family Lamptero- 

 crinidse. 



