262 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



The two individuals from the Aru Islands, which he formerly referred to a new 

 species, Antedon dubia, have about 35 cirrus segments with the later ones carinate as 

 in A. irregularis. But they have relatively large and conspicuous radials with a 

 sculptured surface exactly as in Bell's figured specimen of Antedon decipiens, which, 

 like these, has no IIIBr series. The arm bases of the smaller individual from the 

 Aru Islands resemble those of A. decipiens, while those of the larger show more of the 

 characters of A. irregularis. On the other hand, A. variipinna and A. crenulata both 

 have IIIBr series and 30 or more spiny cirrus segments, while the radials are fairly 

 distinct, those of A. crenulata being more or less sculptured. Neither species has 

 specially rounded arm bases, like those of A. irregularis, though the general outline 

 of the ossicles is the same in all the types. Carpenter said that the variation in the 

 characters of all these different forms may be conveniently expressed by letters as 

 follows: 



Number of cirrus segments 30 to 35 A 25 a 



Character of cirrus segments Distinctly spiny. B Sharply carinate b 



Radials Distinct C Mostly concealed c 



IIIBr series Present D Absent d 



Arm bases Much rounded-.E Less rounded e 



Arms Serrate F Fairly smooth f 



He noted that we then get the following expressions to denote the eight forms of 

 this specific type, five of which have been regarded as representing different species: 



fl. Antedon variipinna ABCDeF Canton] 



2. Antedon crenulata ABCDef Borneo 



3. Antedon decipiens type (Alert) aBCdef Arafura Sea 



4. Antedon decipiens var. (Alert) Abcdef Prince of Wales Channel 



5. Antedon decipiens var. (Challenger) ABcdeF Prince of Wales Channel 



6. Antedon irregularis (Challenger) AbcdEF Prince of Wales Channel 



7. Antedon irregularis (Alert) AbcDEF Torres Strait and 



Prince of Wales Channel 



8. Antedon dubia (Challenger) AbCdEF Aru Islands 



Carpenter said that with these facts before us it is difficult to avoid the conclusion 

 that we are dealing with but one specific type, and this conclusion is confirmed by the 

 fact that in all these different forms the general shape of the brachials and the char- 

 acters of the pinnules are respectively identical, though the latter vary considerably 

 in the degree of development. The distal brachials have the same shape throughout 

 the whole series, as shown in the Challenger examples from the Aru Islands and from 

 Torres Strait. On the other hand, the alternating lateral projections of the ossicles 

 in the lower parts of the arms are very marked in the form from Torres Strait, which 

 Bell called Antedon irregularis, and it is fairly distinct in those from the Arafura Sea 

 and from the adjacent Aru Islands. But it is comparatively insignificant in the other 

 form from Torres Strait, which has much less convex IBr and IIBr series than the 

 irregularis form from the same locality. 



Carpenter said that another universal character of all the different varieties he 

 has referred to this species is the large size of the pinnules on the fourth (that is, 

 fifth) and the two or three following brachials, and the lateral projections at the distal 

 ends of their component segments. P D , when present, is comparatively small, but 

 its successor, P,, is somewhat larger, though that on the next brachial (P a ) is smaller 



