690 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



others are practically impossible to determine either with regard to subfamily or to 

 genus. 



Gisl^n tried to work out and establish some characters of systematic value for 

 the determination of young comasterids, but remarked that this is a very difficult task, 

 for the sj'stematic characters in the comasterids, as in all comatulids, are based on 

 the length, breadth, appearance, and order of magnitude of the calcareous ossicles 

 which combined make up the skeleton of the animal, and these are very different in 

 young and full-grown individuals. He made the following generalizations. 



1. The cirri in all young forms correspond to a type about the same as that 

 characteristic of Comaster serrata or Comatella brachycirra; that is, with about 10 

 segments of which the third and fourth are the longest — two or three times as long 

 as broad. 



2. The division series beyond the IBr series, which furnish characters important 

 from the systematic viewpoint, have not yet appeared. 



3. The younger the animal the greater the relative length of the proximal arm 

 ossicles. This is still more true of the distal brachials. The distal ends of the bra- 

 chials are serrate and everted. 



4. The comb on the proximal pinnules, which aflords very reliable characters 

 in adolescent and full-grown specimens, tends at an early age to become reduced to a 

 uniform type, all small individuals having combs with a few high and rather large 

 teeth. The young of the species of Comaster have combs only on the proximal 

 pinnules. 



5. In the very earliest stages the disk has a central mouth and a marginal anal 

 tube. 



Gisl6n said that as a general rule young comasterids which have a gap in the 

 series of proximal pinnules (excluding forms of the Comatilia type) are impossible to 

 determine even with tolerable certainty. But from a comparative study of the 

 characters presented by the disk it might be possible to determine certain fi.xed 

 points for the appraisal of the systematic position of the animal. 



The young of the species of Comatella and of the large species of Comissia have 

 a central or subcentral mouth and a short, narrow, and inconspicuous anal tube. 

 On the ventral side the skin is tightly stretched between the arms, giving the disk a 

 characteristically lean appearance. The young of Comissia minuia are also in the 

 early stages recognizable by having the ambulacral furrows surrounded with cushion- 

 shaped slopes, probably indicating the extension of the gonads on to the disk, and 

 this condition, together with the characteristic proximal brachials which even at 

 an early stage are very short, the coarse pinnule bases soon thickened by the genital 

 glands, and the smooth proximal portion of the arms, makes them fairly easy to dis- 

 tinguish from young individuals of other species. 



The young of Comaster and of Comantheria in the early stages also have a swollen 

 disk. The anal tube is large, thick and coarse, a little swollen, and often (especially 

 in Comantheria delicata) strongly papLllated or plated. In the species of Comaster the 

 lengthening of the anal tube soon ceases, and in large individuals the tube acquires 

 a characteristic wartlike appearance, while in Comantheria it continues to lengthen 

 into a long large chimney. In smaller young forms the mouth is central, but, except 

 in Comaster serrata, it soon becomes displaced marginally. 



