REPORT ON THE CRINOIDEA. 47 



Bell's method of indicating the varying characters of the cirri is as follows : — 

 " If there are from 1-12 cirri, we may say there are few ; if from 12-30 a moderate 

 number; and if more than 30 a large number; if there are not more than 20 joints to 

 the cirri we may look upon them as being few, if from 20-40 moderate, and if more 

 than 40 numerous. I propose to use the letters a, b, and c to represent few, moderate, 

 and numerous respectively ; while the letter for the number of cirri will form the 

 numerator and that for the number of joints the denominator of a fraction ; and where 

 there is a difficulty of decision one might write ab, or be. Antedon and Actinomet ra 

 may be usefully, though not of necessity, distinguished by making A or A' part of 

 the formula." 1 Bell prefers to use A' for Actinometra rather than "a" as I have 

 suggested, because the a is used in the formula for the cirri. I do not see the 

 force of this objection, as the two letters occur at opposite ends of the species formula 

 and only the later one is italicised ; while A' is much too like A to be readily distin- 

 guished at a glance, apart from the possibility of printer's errors. Bell's suggestion 

 that "br." should be used instead of "b" for the brachials to avoid confusion with 

 the b of the cirrus-formula is a good one, however, and I have adopted it accordingly. 

 In my former method of formulation I denoted the presence of ten arms only by 

 inserting a 10 into the formula of the type, thinking it more convenient to indicate this 

 character, which is generally a sharply defined one, in a positive, rather than in a negative 

 manner. Bell thinks, however, that "A. 10" compared with "A. 3 " is very apt to 

 mislead and to give rise to the impression that the Antedon in question has ten distichal 

 joints. In deference to his scruples therefore I shall omit the 10 in future and write, as 

 he does, the specific formula of ordinary ten-armed Coniatuke like Antedon eschrichti, 

 with no other characters than the generic letter and the cirrus-fraction. Thus Antedon 



be 

 phalangium is represented by A.—. 



It often happens that some individuals of a species are more fully developed 

 than others, i.e., they have additional axillaries in the arm-divisions. Thus for 

 example, one or two bidistichate series are occasionally present in Antedon lusitanica 

 which usually only has ten arms (PI. XXXIX. figs. 1, 3); while palmars are sometimes 

 found in some forms of Antedon quinquecostata and of Antedon variipinna, but not in 

 others (PL XXXVIII. fig. 1 ; PL XLIX. fig. 1). Under these circumstances I write 

 the figure or letter which denotes the character that is variable between brackets, 

 e.g., A.(2), lusitanica; A.2.(2), quinquecostata; A.[3.(2)], variipinna. 



In Bell's system, however, " when a character frequently though not always obtains, 

 the corresponding letter is put within brackets." 2 If this were only meant to imply that 

 certain characters present themselves in some individuals of a species, but not in others, 

 Bell's method would be the same as mine. But though he goes much further than I 



1 Loc. cit., p. 531. -' Loc. tit., p. 532. 



