18 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



The fomatulids alone in their numbers, m the diversity of their habitat, and 

 in the complexity of their systematic interrelationships are in the jjresent seas 

 (he strict sj'stematic equivalent of each of the other classes of echinoderms. Of 

 themselves thej' form what is unmistakably a class, with all the distinctive systematic 

 features of a true class. 



Thus the comatulids, in reality only an insignificant and aberrant offshoot from 

 the general phylogcnetic crinoidiil line, represent m their relationsliips to the other 

 organisms of the seas of the present day a true class, exhibiting the curious anomaly 

 of a grouj) which, considered from one pomt of view is a tmo class, but considered 

 from another i)oint of view does not even rise to the dignity of a subfamily. 



ILLUSTRATIONS. 



A verj' considerable amount of time and thought has been expended in attempts- 

 ing to solve the problem of how best to illustrate the various species of comatulids. 

 These animals differ but slightlj' in their general build, though very greatly in the 

 finer details of their structure. 



In the CliaJIengcr monograph the first serious attempt was made to portray 

 the comatulids in a monograpliic waj'. Although the figures are exceptionally 

 good, there has always been more or less difficult}' in comprehending them, and I 

 experienced a great deal of trouble with them myself. It was not at first evident 

 wherein tliis difficidty lay. A certain inabOit}'' of the artist to grasp the significance 

 of such details as the smooth or comparatively rugose appearance of certain speci- 

 mens, details exceptionally difficult of portrayal in a satisfactory manner, account 

 for much of the indefiniteness of certain figures, while the varied position of the 

 arms in the examples given make comparisons between the illustrations exceedingly 

 laborious, and undoubtedlj' accounts for the rest. 



The figures in Ilartlaub's works were drawn bj' a different artist than were those 

 in the CliaUengcr report; though exceUent dcfineations, a certain personal element has 

 ent«red into their make-up which makes comparison between them and the Challenger 

 figures more or less unsatisfactory. 



No personal element entered into Doderlein's beautiful photographic repro- 

 ductions; yet they are as difficult to compare A\nth the figures of Carpenter or of 

 Ilartlaub as these arc with each other. It was therefore evident that I could not 

 hope to produce satisfactory results by placing sole reliance either upon the artist 

 or upon the camera. 



A study of Doilcrlein's paper side bj'' side with the Challenger report suggested 

 to me that if each sjiecies were drawn in detail, and a photographic reproduction 

 of the specimen also given, the former to show the intricate structure and the latter 

 to give the general appearance, a result might be attained which would stand a good 

 chance of being fairly satisfactory. 



After a mature consideration of the matter I decided that, as i)hotographic 

 plates were also to be used, there was no object in burdening the text figures vnth 

 detail; the simi)lcr they were the more forcibly could the essential differential 

 characters be made to stand out. Moreover, if all the figures were rendered semi- 



