18 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



The comatulids alone in their numbers, in the diversity of their habitat, and 

 hi the complexity of their systematic interrelationships are in the present seas 

 the strict systematic equivalent of each of the other classes of echinoderms. Of 

 themselves they 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 phylogenetic crinoidal line, represent in their relationships to the other 

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

 of a group which, considered from one point of view is a true class, but considered 

 from another point of view does not even rise to the dignity of a subfamily. 



ILLUSTRATIONS. 



A very considerable amount of time and thought has been expended in attempt- 

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

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

 finer details of their structure. 



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

 the comatulids in a monographic way. Although the figures are exceptionally 

 good, there has always been more or less difficulty in comprehending them, and I 

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

 wherein this difficulty lay. A certain inability 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 undoubtedly accounts for the rest. 



The figures in Hartlaub's works were drawn by a different artist than were those 

 in the Challenger report; though excellent delineations, a certain personal element has 

 entered 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 with the figures of Carpenter or of 

 Hartlaub as these are 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 Doderlein's paper side by side with the Challenger report suggested 

 to me that if each species 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 photographic 

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

 detail; the simpler they were the more forcibly could the essential differential 

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



