British Fossil ( 'rinoids. 389 



but here we must pause to consider what that statement 

 means. 



In l'JOO (Lankester's 'Zoology/ vol. iii.) I divided the 

 Flexibilia Impinnata into the families [chthyocrinidae, Taxo- 

 crinidae, Dactylocrinidae, Sagenocrinidse, and the douhilul 

 Grazacrinidae. Omitting the last-mentioned, Dr. F. Springer 

 (Oct. 1906, Journ. Geol. vol. xiv. p. 516) adopts an arrange- 

 ment of genera based on essentially the same principles, 

 which his increased knowledge has enabled him to render 

 more precise and to apply with greater correctness. The 

 chief difference of principle is the division of the genera 

 according as the anals are united with the adjacent rays by 

 direct suture or by finely plated integument (perisome). 

 Further, Dr. Springer attaches rather less importance to the 

 mode of arm-branching, and lays greater stress on the 

 number of primibrachs. The increase of knowledge is mainly 

 as regards the anal plates. 



Thus, in the Family Taxocrinidae Dr. Springer now includes 

 several g nera with heterotomous, ramuliferous arms, which 

 I placed in the Dactylocrinidae. On the other hand, be 

 transfers Anisocrinus and Homahcrinus from the Taxo- 

 crinidae, with Calpiocrinus, LitJiocrinus y and Dactylocrinus 

 from the Dactylocrinidae, to the Family Sagenocrinidse, 

 which thus becomes a trifle unwieldy, not to say hetero- 

 geneous. 



I am prepared to adopt the mode of union of the anal 

 series with the rays as a basis of classification, and therefore 

 agree in restricting the Taxocrinidae to genera that have the 

 anal plates more or less separated from the adjacent rays by 

 perisome. But it still seems to me convenient to exclude 

 from that Family the genera with heterotomous arms. 1 

 would therefore suggest the following diagnosis: — 



Family Taxocrinidae. 

 Impinnata with anal plates forming a well-defined vertical 

 series more or less separated from the adjacent rays by peri- 

 some ; with isotomous aims, which may abut but do not 

 interlock, and are generally divergent; with few inter- 

 brachials. 



The genera are (a) those with a radianal, viz. : 

 Protaxocrinua Springer, genotype P. oralis (Aug., s. Taxo- 



crinus). 

 Gnorimocrinus W. & Sp., genotype G. c.rpansus (Aug., 



s. Ta.cocrinus). 

 Meriatucrinus Springer, genotype M- loveni (W. & Sp., 



s. Gnorimoo inus). 



