122 Reviews — Wachsmidh 6f Springer's Monograph on Crinoids. 



Diabolocriniis (p. 249), Ordovician, a Rbodocrinirl in which tlie 

 interbrachials consist of larger plates surrounded by smaller ones, 

 the anus is at the end of a tube, and the arms bear ramules. 



Perigli/ptocriiius (p. 277), Ordovician, a Glyptocrinid with large 

 basals and biserial arms. 



Eutrochocrinus (p. 408), with genotype Batocrinus Ghristyi, Dizi/go- 

 crinus (p. 413), with genotype B. indianensis, Lobocrtnus (p. 434), 

 with genotype B. Nashvillcs, and Macrocrinus (p. 446), with geno- 

 type B. Koninchi, are closely allied genera of Batocriaid?e (s.str.) 

 and all Lower Carboniferous. 



Aorocrinus (p. 470) is a Devonian and Carboniferous predecessor 

 of Dorycrinus and Agaricocriniis ; the genotype is D. immaturus. 



Acacocrinus (p. 615) is a Siluiuan subgenus of Carpocrinus, for the 

 reception of A. Elrodi and A. americnniis, but is worthy of generic rank. 



Cactocrinus (p. 600), with genotype Actinocrinus pi-oboscidialis, is 

 separated from Actinocrinus because the arm-rami are given off in 

 a continuous circlet around the theca, clearly separating the teginen 

 from the cup : the name is due to the spines on tegmen and arms; 

 those on the pinnules imbi'icate over those of adjacent pinnules. 



Camptocrinus (p. 779) differs from Dichocrinus, under which it is 

 placed subgenerically, in the structure of the stem, which is modified 

 like that of Hall's Myelodactylus and Salter's Herpetocrinus. Campto- 

 crinus is in the Keokuk and Kaskaskia groups. Similarly modified 

 stems were possessed by Poteriocrinidte of Kaskaskia age. There is 

 therefore room for doubt whether the European Herpetocrinus really 

 is congeneric with the American Myelodactylus. No detailed account 

 of the stem of Camptocrinus is given, so that one cannot ascertain to 

 what extent it agrees with that of Herpetocrinus. 



These genera, as well as the new species described, appear to have 

 been established with care, and may safely be accepted. The 

 principles guiding the authors are thoroughly in accordance with the 

 most appi'oved modern views. They recognize the corollary of the 

 theory of descent, namely, that the taxonomic value of a character is 

 in proportion to its persistence and not to its physiological im- 

 portance (p. 153). Still no single character is absolutely constant, 

 " and the larger our collections the less persistent and fixed will we 

 find the separate characters. But if we are reasonably happy in our 

 identifications, we may expect to find greater reliance to be put upon 

 the correlation of characters, so that while one or more of them will 

 show a tendency to departure, the sum of all will exhibit a pre- 

 dominance which will hold the form in question within the given 

 group." Characters cannot be sorted out as of ' family,' ' generic,' 

 or 'specific' importance, but the value or rank of a character "is 

 proportional to the extent to which it tends to combine subordinate 

 groups." Later on (pp. 155, 156) the difficulties attaching to the 

 sejjaration of species are discussed, and the necessity for appreciating 

 stages of growth, limits of individual variation, and abnormalities is 

 emphasized. Valuable illustrations of these difficulties will be found 

 under Teleiocrinus umbrosus (p. 629) and under Platycrinus (pp. 652, 

 680, 681). The modifications due to individual growth in the latter 



