386 Mr. F. A. Bather on British Fossil Crinoids. 



a scaffolding necessary for the erection of that more solid 

 structure to which it must one day give place. 



EXPLANATION OF PLATE XV. 



(Illustrating chief types of Arm-structure in Fistulate Crinoids.) 



While the figures of this Plate are necessarily diagrammatic, they have 

 been constructed either from actual specimens or from the best published 

 drawings obtainable. Their order is merely intended to facilitate com- 

 parison and follows no scheme of classification. It is not possible to 

 indicate in such a Plate the various degrees of articulation, but in figures 

 7 & 20 syzygies are represented by dotted lines. In each figure the radial 

 is drawn in whole or in part. In the following notes the specific name is 

 inserted when that particular species has served as copy for the diagram ; 

 other species of the genus have of course the same general structure. 

 In the case of a genus not actually figured, the number indicates the type 

 to which it approximates in aim-structure. 

 Achradocrinus — arms unknown. 

 Agassizocrinus — 15 ; long, stoutish ; ossicles short, cuneate ; pinnules 



strong. 

 Ampheristocrinus — one brachial only known, quadrangular and very 



small. 

 Anomalocrinus — 11 ; figure based on description by W. & S. Rev. III. 



(212) Proc. 1886, p. 136. 

 Arachnocrinus — 3 ; heavy, scarcely diminishing towards tips ; ossicles 



short, quadrangular, but axillaries longer. 

 Atelestocrinus — 10 ; armlets from every 2nd ossicle, on alternate sides, 



extend to tips of arms. 

 Baerocrinus Ungerni — 1 a ; after Grewingk, from P. H. Carpenter, Quart. 



Journ. Geol. Soc. xxxviii. pi. xi. fig. 1. 

 Barycrinus — 10 ; arms sometimes branch again on 3rd or 4th distichal, 



but never in anterior ray, and only in one arm to a ray ; in B. 



tumidus (?) the antero-lateral rays have only one main arm 



apiece. 

 Belemnocrinus typus — 20 ; see W. & S. Rev. III. 1885, pi. v. fig. 10. 

 Botryocrinus ramossissimus — 9 ; after Angelin, op. cit. pi. xx. fig. 8. 

 Botryocrinus sp. nondescr. — 13 ; from specimens from Dudley. 

 Biirsacriuus — arms branch, and are in contact laterally; distichals wide, 



flat, slightly cuneate ; palmars less than half the width. W. & 



S. consider this so close to Graphiocrinus that they have .made 



it a subgenus thereof; otherwise its place would seem to be with 



the Scaphiocrinites, near Woodocrinus, from which it differs in 



the more advanced condition of the anal area. "Without seeing 



specimens I do not like to venture on the alteration. 

 Calceocrinus — pinnules not developed ; lateral arms dichotomize in a 



peculiar manner, out of the ordinary line of evolution. 

 Carabocrinus — 3; arms short compared with size of cah"x. 

 Castocrinus — arms irregularly dichotomous, non-pinnulate. 

 Catittocrinus — arms simple, not branched, many rise from a single radial 



as shown in PI. XIV. fig. 29. 

 Ceriocrinus — 15. 

 Closterocrinus — arms obscure, see Hall, Pal. N. Y. vol. ii. p. 179, pi. xli a. 



figs. 2 a-f. 

 Codiacrinus—3 ; see Follmann, " Unterdevonische Crinoiden," Verb. d. 



nat. Ver. preuss. Rheinl. xliv. pi. iii. fig. 1, 1887. 



