A. H. CLARK : THE OBINOIDS OF THE INDIAN OCEAN. 121 



HETEROMETRA REYNAUDII. 



Comatula (Alecto) reynaudii 1846. J. MUller, Monatsber. d. k. preuss. Akad. d. 



Wiss., 1846, p. 178. 

 Antedon variipinna 1904. Chadwick, Report Pearl Oyster Fisheries Ceylon, 



part 2, Supplementary Report xi, p. 157. 

 Heterometra reynandi 1909. A. H. Clark, Proc. Biol. See. Washington, vol. 22, 



p. 11. 



Localities.— -SoM^A of Ceylon (6° 01' N. lat., 81° 16' E. long.) ; 34 fathoms. — 

 Four specimens, one small and two medium sized, the cirrus segments number- 

 ing 31-36. The fourth specimen is one of the most interesting crinoids I have 

 ever seen. The centrodorsal and division series are of normal size and shape ; 

 one cirrus remains, which tapers to a point at the seventeenth segment ; no dor- 

 sal spines are developed ; the nineteen arras are only 17 mm. long, of normal size 

 basally but rapidly tapering to a point beyond which they are continued for a 

 short distance in a slender soft uncalcified process. The lower pinnules taper 

 very rapidly for the first five or six segments, from that point onward being very 

 hair-like and slender with little or no lime in their composition. Beyond the arm 

 bases the pinnules are exceedingly slender, with never more than the first or first 

 two segments of normal size, and usually with none, usually with traces of 

 calcareous deposits showing segmentation, though often quite without any. With 

 the reduction of the calcareous matter in the pinnules comes a reduction in the 

 pinnule sockets, the non-calcareous pinnules on the outer part of the arm not 

 being accompanied by any modification in the outer edge of the brachials what- 

 ever. Most of the arms of the specimen have been broken off and repaired at 

 the syzygy between the third and fourth brachials. 



The short, stout, rapidly tapering arms which, as it happens, are folded 

 inward over the disk, are strongly suggestive of those of the fossil Flexi- 

 bilia Impinnata, a similarity which is greatly enhanced by the almost complete 

 absence of calcified pinnules, and the entire absence of pinnule sockets on the 

 outer part of the arms. Had this specimen been found fossil it would probably 

 have been referred to that group ; as it is it leads one to suppose that the so- 

 called Impinnata may not, after all, have been impinnate as commonly con- 

 sidered but may have been supplied with non-calcareous pinnules which were 

 never preserved. The Impinnata all have a large visceral mass and short arms, 

 just as in this specimen, and it is somewhat problematical how they managed to 

 obtain sufficient food to maintain their existence; but if, on the analogy of this 

 specimen, we increase their arm length by supplying a hypothetical non-calcare- 

 ous continuation of the arms, and then supply the whole structure with soft 

 pinnules, we can readily furnish the animals with an adequate food-collecting 

 area. 



Mr. Frank Springer is now completing his monograph upon the Flexibilia. 

 I therefore referred the specimen to him for study in connection with his work, 



