54 Mr. F. A. JlaihcY—Sitf/'jesfed 



to formulate the laws of arm-branching in the various families 

 or genera. The difficulties are of two kinds, subjective and 

 objective. We will take them in that order. 



The subjective difficulties are due chiefly to the cumbrous, 

 illogical, and, for the most part, meaningless nature of the 

 terms adopted. This is not a censure of any one in parti- 

 cular, for no one man could ever have invented such a discon- 

 nected lot of names for similar and connected objects. The 

 terminology has grown up bit by bit, unsubjected to the stern 

 laws of natural selection. It is by no means easy for the 

 student, or even for the describer of new species, to carry all 

 these names in his head. It is on the face of it absurd to 

 begin a fresh series of numbers at the postpalmars, as though 

 there were some morphological change ; moreover, the inter- 

 pretation to the mind of such a phrase as " the second post- 

 palmars" involves an arithmetical calculation before one realizes 

 that the ossicles alluded to are brachials of the fifth order. 

 Then, in speaking of a particular ossicle, one can hardly say 

 " the second third postpalmar," so one is obliged to indulge 

 in some such cumbrous circumlocution as '' the second ossicle 

 in the third postpalmar series." The symbols too that are 

 employed in specific formulffi — c, d, 2y,p',p^% b, &c. — hardly 

 convey their meaning at a glance, while they certainly do 

 not lend themselves to the expression of statements referring 

 to more than one order of brachials at a time. It is of course 

 possible that these difficulties are not obvious to higlily trained 

 intellects, and it is true that they hardly present themselves 

 in the study of most recent Crinoids. 



There is, however, a more serious objection, at least to one 

 of the terms. It was J. S. Miller who invented the now 

 resuscitated term '' costals," and it is true that he used it to 

 denote the second radials, where he did not call them arm- 

 plates. But, as can be seen from the table that was given by 

 Carpenter {op. cit. p. 16), he also applied the term to the first 

 radials, the basals, and the infrabasals. It would no doubt have 

 been legitimate to restrict the term to one or other of the plates 

 to which it was ajiplied by Miller ; but unfortunately this 

 had ahead}' been done. As Carpenter himself pointed out, 

 Prof. Loven has " proposed to specialize this name as denoting 

 the primary interradial plates of the Echinoderm apical 

 system, i. e. the genitals of Urchins and the basals of 

 Crinoids." It niay be true that Prof. Loven's proposal " has 

 not been generally accepted by Echinologists ; " at the same 

 time there are others who have a])i)lied the term " costals " to 

 interradially disposed ])lates, notably Prof. James Hall, who 

 has thus denoted the basals of various species in the ' Pakvou- 



