A MONOGRAPH OF THE EXISTING CRINOIDS 381 



Remarks. — Whether discoidea should be recognized as a species distinct from 

 tessellata, or as a geographical race, or perhaps merely as a form, is at the present time 

 simply a matter of personal opinion. Although when they are typically developed 

 tessellata and discoidea are very different in appearance, they certainly intergrade. 

 The ranges of the two types overlap, though generally speaking tessellata is character- 

 istic of the region from the Sunda Islands to the Moluccas and southward along the 

 coast of Western Australia, while discoidea is equally characteristic of the region from 

 the Philippines to Singapore and eastern and northern Australia as far as the Aru 

 Islands. 



Dr. August Keichensperger said in 1913 that the similarities between typical 

 tessellata and the Australian discoidea are so great, while on the other hand the differ- 

 ences, which have to do only with the relative width of the cirrus segments and a few 

 cirrus segments, are so slight and so variable, that one can scarcely regard tbe two 

 forms as species; at most they can be considered as local varieties. He said that he 

 kept discoidea distinct from tessellata only to avoid increasing the present (1913) 

 confusion in the taxonomy of the comatulids. He remarked that the small specimen 

 from Merton's station 16 seemed to him to cast doubt on the possibility of establishing 

 new species on the basis of differential characters furnished by the cirri. His view is 

 that as the cirrus segments change the relation of length to breadth during growth the 

 cirri afford specific characters of only very limited value. He also noted that the 

 number of pinnule segments is not fixed, and synarthrial tubercles are much less 

 strongly developed in small than in large individuals. He believed that, in view of 

 the detailed descriptions given of their specimens by Carpenter and by Hartlaub, 

 supplemented by his study of the large specimen of tessellata from Amboina, the most 

 reasonable assumption is that the various so-called species really represent a kind of 

 developmental series. 



In the present state of our knowledge the identification of comatulids in very 

 many cases is practicable only if adults are available for study. This is particularly 

 true in the case of species with more than 10 arms. 



But the fact that a small individual of discoidea differs widely in cirrus and pin- 

 nule characters and in the relative development of the synarthrial tubercles from an 

 adult is no indication that it would not be distinguishable from a small individual of 

 tessellata in the same stage of development. In many different animal types growth 

 changes are as far reaching as they are in the crinoids, and in not a few groups that 

 are much better known than the comatulids accurate identifications are possible only 

 if adults are available. 



Dr. Torsten GislSn (1919) entirely agreed with Dr. Reichensperger that it is 

 incorrect to maintain discoidea and tessellata as distinct species on the ground of the 

 somewhat different cirrus segments. 



Localities. — Takao, Formosa (Taiwan); Dr. Fred. Baker, December 3-4, 1914 

 [A. H. Clark, 1912, 1918] (1, U.S.N.M., 34497). 



Port Galera, Mindoro, Philippines; Dr. Lawrence E. Griffin (2, M.C.Z., 680). 



Albatross station 5432; in the vicinity of eastern Palawan; Corandagos Island 

 (N. W.) bearing N. 30° E., 5. 7 miles distant (lat. 10°37'50" N., long. 120°12'00" E.); 

 93 meters; sand; April 8, 1909 (1, U.S.N.M., 36010). 



