730 



686 "thktis" scientific kksults. 



e^. AH tlie pinnules cylindrical. 



J^. Brachials in distal part of arm exceedingly short 



and discoidal (10-40 arms) Ilimerometrince.- 



f. Brachials in distal part of arm wedge-shaped and 

 not particularly short. 

 g^. The outer cirrus segments bear dorsally paired 

 dorsal spines, or one or two denticulate trans- 

 verse ridges (10-40 arms) Golohomttridce. 



gf'. The outer cirrus segments are longitudinally 

 carinate dorsally, or bear single median dorsal 

 spines. 



A^. II Br 4 (3 + 4) Himerometridx. 



A2. II Br 2. 



»*. Pq very stiflf and spine like, with eighteen 



or fewer segments Stephaiiometrida. 



i^. P3 flagellate distally, with more than 



twenty segments Manametridce. 



Key to thk Genera of the Comasterid^. 

 a^. Combs not confined to the proximal pinnules, but occurring at 

 intervals all along the arm ; proximal pinnules slender ; mouth 



but slightly excentric Comaster. 



a^. Combs confined to the proximal pinnules ; proximal pinnules 

 stouter tlian those succeeding. 



b^.ll Br4('3-F4) ; always more than 10 arms Comanthus^ 



6*. II Br 2, or lacking ; 10 or more arms. 



c*. Middle pinnules stout, with segments which are very 

 much broader than long ; I Br apparently united by 



syzygy ; if more than ten arms, cirri are absent Gomatida. 



c^. Middle pinnules not enlarged, composed of approximately 

 squarish segments ; I Br united by synarthry ; twenty 

 or more arms ; cirri well developed Comatella. 



Key to the Geneka of the ColobometriDjE. 

 a^. Pa absent. 



h^ All the pinnules very stiff, with very spinous distal ends to 

 the segments ; all the lower pinnules enlarged ; cirrus seg- 

 ments, or P2 and Pg, with very spiny ends, forty or more in 



number Colohomttra^ 



b'^. Po only enlarged and stiffened ; cirrus segments with smooth 

 ends, less than twenty in number. 



c^. More than ten arms Cyllometra. 



c^. Ten arms Decamtiru. 



a'. Pn present. 



b^. Ten arms ; 20 or less cirrus segments, the outer with dorsal 



transverse ridges Oligomttra. 



62. More than twenty arms; more than 30 cirrus segments, the 



outer with paired dorsal spines. Genometra, 



Key to the Genera of the Thala.ssometrid^. 

 a^. Ten arms ; cirri arranged in ten columns on a rather small 



columnar centrodorsal ; Pi larger and stouter than Pj., .Stiremelrcu 



