16 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Asterotnetra anthtu, arms 85 nun. long: (12) 14 brachials 1.6 mm. broad in each 

 in mm. in the proximal part of the arm, and (15) 18 brachials l.l mm. broad in the 

 distill; relation of the longer side of the brachials to width L:2 to 2:3; angle of the 

 distal articulations with the longitudinal axis of the arm 69-77°. 



/' odontometry boeki, arms (id nun. long: (11) 12 brachials 1.3 mm. broad in each 

 10 mm. in the proximal part of the arm, and (14) 1") brachials 0.7 mm. broad in the 

 distal; relation of the longer side of the brachials to width (3:4 to) 1:1; angle of the 

 distal articulations with tin- longitudinal axis of the arm 69-75°. 



Antedon petasus, arms 7."> mm. long: (12) 15 brachials 1.2 mm. broad in each 10 

 nun. in the proximal part of the arm. and (14) 17 brachials 1.0 mm. broad in the distal; 

 relation of the longer side of the brachials to width 1:1 ; angle of the distal articulations 

 with the longitudinal axis of the arm 64-75°. 



Heliometra glacialis, arms 200 mm. long: (7) 9 brachials 3.2 mm. broad in each 

 10 mm. in the proximal part of the arm, and (12) 15 brachials 1.5 mm. broad in the 

 distal; relation of the longer side of the brachials to width 1:2 to 2:3; angle of the 

 distal articulations with the longitudinal axis of the arm 68-78°. 



Pctiometra prolixa, arms about 100 mm. long: (9) 12 brachials 1.6 mm. broad in 

 each 10 mm. in the proximal part of the arm, and (11) 14 brachials 1.0 mm. broad in 

 the distal ; relation of the longer side of the brachials to width 1:1; angle of the distal 

 articulations with the longitudinal axis of the arm 66-74°. 



Pentametrocrinua diomedeae, arms 90 mm. long: (10) 13 brachials 0.6 mm. broad 

 in each 10 mm. in the proximal part of the arm, and (11) 14 brachials 0.5 mm. broad 

 in the distal; relation of the longer side of the brachials to width 3:2 to 2:1; angle of 

 the distal articulations with the longitudinal axis of the arm 59-66°. 



Gislen said this study showed that distinctly oblique articulations, that is, artic- 

 ulations in which the articular line makes an angle with the longitudinal axis of the 

 arm of from 59° to 79° (average 71°), are found in the Comasteridae (exclusive of the 

 rinae and ( 'a pillaster), Thalassometridae, Charitometridae, and Calome- 

 tridae. and in the Macrophreata ; while on the other hand indistinctly acute to right 

 angles of from 72° to 90° (average about 83°) are found in the Comasterinae, C'iij>il- 

 laster, the Zygometridae, Himerometridae, Mariamctridae (including the Stephano- 

 metridae). Tropiometridae, and Colobometridae. 



lie said that from the figures gi\ en it may also be seen that the number of brachials 

 for each 10 mm. and their relative length has a certain relation to the thickness ol the 

 ami- that is, generally with the size of the animal. In the majority of cases, how- 

 ever, the greatesl number of segment- in each 10 mm. and the shortest segments with- 

 out comparison are found in the group in which the articular line makes nearly a 

 right angle with the longitudinal axi- 



The figures given are from the middle or distal parts of the arms. The figures 

 foT\tn • the -i/r ,,f the angles in the proximal parts of the arms. As in the 



previous cases the figures are taken from the distal borders of the brachials and refer 

 to the angles of tin' pinimlate side. Figures omitted denote hypox.yg.-il-. 



Comanthw japonica: lll'.r.. 80°; IlIBr 2 -78°; brachials 1-110°; 2-87°; 4-84°; 

 5-90°; 6-84°; 7-S0°; 8-78°; 9-76°; 10-78°; 11-78°; after the twenty-third brachials 

 the angles are larger, up to 85° or 90°. 



