30 T. GisLÉN, 



Finally a few words about the relation bet\\een the genera Co- 

 matella and Gomissia. When A. II. Clark in I'JOO propf)sed these two 

 genera he characterized the iirst-inentioned one (Smiths. Misc. Coll. 

 Vol 52 p. 207) thus, that species belonging to this genus siiould have 

 the first syzygy between Br 3 and 4 in arms situated on 1 lii'ax, but 

 the first syzygy between Br 1 and 2 in arms coming from axillaries of 

 higher numbers. According to Clark's view some arms should thei'e-: 

 fore be divided by »extraneous» some others by »intraneous division» 

 and thus one might in this genus have crinoids with so-called »com- 

 pound arms». In the later proposed species Comatella decora Clark 

 has found a syzygy between Br 2 -f 3 or on the outer side of the arm- 

 divisions between Br 3 -f 4. Comatella brachycirra mihi usually, but far 

 from always, has Br 1 -)- 2 on tlie inner side, 3 + 4 on the outer side of 

 the arm-divisions. The specimens of G. maculata and C. stelligera that I 

 have investigated usually have Br 1—2 3+4, in the case both of the 

 inner and outer side of the division-series; in a few cases, however, 

 we find Br 1+2. — Most often, therefore, the »compound» nature of 

 the arms is visible, but by no means always. From what is mentioned 

 above it is evident that the compound nature never appears in X- 

 armed young GomateUas. How are then the latter to be distinguished 

 from the genus Gomissia, the species of which always have X arms? 

 As to this A. H. Clark in the Siboga Exp. Vol. 42 B, p. 23 has re- 

 marked that the young of Gomissia can be distinguished from the X- 

 armed young of other genera by very shoit and broad I Br-series, the 

 ossicles of which are said to be united in very close articulation. As I 

 have tried to show in describing Gomissia ignoia minuta this only holds 

 good in full-grown specimens of the species. The small young of large 

 Cowissia-species might therefore have rather long I Br-segments and 

 are consequently similar to young GomateUas. Just as the immanent 

 tendency to »compound arm-division» did not appear in X-armed young 

 GomateUas it cannot, if it exists, assert itself in CoH/f.ssm-species which 

 never reach beyond the X-armed stage. In reality, therefore, the dif- 

 ference between the genera turns out to be a difference between a 

 group of X-armed and a series of multibrachiate forms of Gapillasterinœ. 

 Joint characteristics by which both the genera are distinguished from 

 other genera within the subfamily are as follows: Pj on Br 2, short 

 Br-segments, complete pinnulation, cirri of normal comasterid type, at 



