Reviews — Wachsmuth 8^ Springer's Monograph on Crinoids. 323 



warranted. The terms were open to criticism on the following 

 grounds : want of congruity inter se ; previous uses of the word 

 * costal ' in various other senses ; difficulty of remembrance and of 

 working, especially in the higher series; inadaptability to symbols, 

 formulae, and general statements. The truth of this criticism has 

 never been contested, nor has any objection, other than on the 

 ground of novelty, ever been raised to the series of terms and 

 symbols proposed by me in their place, viz., Primibrachs 

 (I Br), Secundibrachs (II Br), Tertibrachs (III Br), Quartibrachs 

 (IV Br), and so on, along with which go the terms and symbols 

 applied to the successive axillaries, Priniaxil (I Ax), Secundaxil 

 (II Ax), and so on. Had I confined myself to the above criticism, 

 and to the proposal of this simple, congruous, easily remembered, 

 and easily applied set of terms, it is probable that they would have 

 met with more general acceptance than has been their lot. 

 Unfortunately, I thought it necessary to draw attention to a morpho- 

 logical difficulty in the way of homologizing the series of a pinnulate 

 arm with those of a non-pinnulate arm ; and to avoid this I proposed, 

 for pinnulate arms only, "a terminology congruous with the 

 Miillerian term ' distichals,' " viz., monostichals, distichals, 

 tetrastichals, octastichals, and so forth. To this latter terminology 

 various objections either have been or might be raised. In the first 

 place, the morphological difficulty, though still obvious to me, 

 does not appear to present itself to Messrs. Wachsmuth and Springer. 

 Secondly, the terms in their higher series, though rarely required, 

 rapidly increase in cumbrousness. Thirdly, the branching of 

 pinnulate arms is often so irregular as to falsify the terms, e.g., 

 instead of their being four rami of the third order there may be only 

 three, which therefore cannot correctly be called tetrastichals. 

 Fourthly, the terms cannot be readily intelligible to the systematist, 

 if he really is so devoid of classical culture and mathematical 

 training as my critics maintain. For these reasons I do not propose 

 to put into practice what has never been more than a suggestion. 

 There are, I still believe, cases in which the distinction between 

 pinnulate and non-pinnulate arms requires expression in the 

 terminology and formulge, and the term ' main-axil ' is undoubtedly 

 of great use. But for general purposes I, like Wachsmuth and 

 Springer (p. 77), "see no good reason why the former terms 

 [primibrachs, secundibrachs, etc.] could not be used for all Crinoids, 

 pinnulate or non-pinnulate." It is greatly to be wished that 

 all writers on crinoids should agree on this matter, and to that end 

 I make this concession. 



We turn now to the " Morphological Part." 



This is almost confined to the morphology of the skeleton, and begins 

 by dividing the skeletal elements into (a) primary and (h) secondary 

 or supplementary, (a) being subdivided into (i) abactinal and 

 (ii) actinal. These categories, established in the paper on " Perisoraic 

 Plates" above referred to, were explained to readers of the Geological 

 Magazine in the review of that paper (May, 1891} ; they are 



