124 Reviews — Wachsmuth 8^ Springer'' s Motiograjyh on Crinoids. 



represent the beliefs of its authors in these matters. They say, 

 it is true, " We have arranged our descriptions so as to place species 

 which are most closely related next to each other" (p. 156). But 

 if they have done this, it has been in a very obscure fashion ; and 

 the same principle is far from being extended to genera. The 

 species of Platycrinus have been arranged in groups around certain 

 typical species : without some such device the crowd of them would be 

 unmanageable. But one would have liked some key to the arrange- 

 ment, and an extension of the method to other genera. Consider 

 the species of Batocrinus ! The account begins with two allied 

 forms from the Warsaw Limestone ^ ; then come four, possibly allied 

 to one another but not to the preceding, from the Lower Burlington 

 of Iowa ; then species from the base of the Lower Burlington of 

 Missouri, one of them approaching Dizygocrinus, another near 

 Lobocrinus and Eretmocrinus ; next come two interrelated species 

 from the Kinderhook, from which we jump to quite a different form 

 in the Upper Burlington, then down again to its ally in the Lower 

 Burlington; then some species, the mutual relations of which are 

 not stated, from the Keokuk, and so back to Upper Burlington. 

 There may be a reason for this erratic promenade ; but if so, it 

 should be stated. Again, under Teleiocrinus, T. adolescens, though 

 said to be the species most closely allied to Cactocrinus, is dealt 

 with furthest away from that genus. One begins to long for the 

 simplicity of the alphabet. So too with the genera. Aorocrinus is 

 described after Dorycrinus, though it is admitted to be its ancestor. 

 Similarly Physetocrinus is held to give rise to Strotocrinus, and 

 Cactocrinus to Teleiocrinus ; but the order of treatment is — Physeto- 

 crinus, Cactocrinus, Teleiocrinus, Strotocrinus. 



After the richly deserved blame which is awarded to other writers 

 for not marking the relations of their species, one would at least 

 expect some words of comparison to accompany each description. 

 The frequent absence of this would not so much matter, did the 

 authors condescend to follow the example of Linneeus and give 

 a diagnosis of each genus and species. Instead, one has often to 

 wade through a page or more of description, comparing it word by 

 word with other descriptions, in order to find out the truly diagnostic 

 characters. This is a fault so common that it may seem pedantic to 

 notice it. So much the worse ! 



It must be admitted that, so far as genera are concerned, the 

 authors have done their duty in the way of providing analytic keys. 

 As these will probably be referred to by many students, it may be 

 as well to point out some inconsistencies. In the analysis (p. 188) 

 Ptychocrinus is said to have 10 arms ; the description (p. 197) says 

 " 10 to 12 "; but according to the descriptions and figures of species 

 the rami are at least 20. In the analysis of Rhodocrinidge (p. 215) 

 it should be noted that Gilbertsocrinus has no anals, and that Lyrio- 

 crinus may have an anal, a correction that makes the divisions 



1 Eeaders of the Geological Magazine scarcely need to be reminded that the 

 order of the stratigraphic groups, from above downwards, is : Kaskaskia, St. Louis, 

 "Warsaw, Xeokuk, Bmiiugtou, Xinderhook. 



