16 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Asterometra anthus, arms 85 mm. long: (12) 14 brachials 1.6 mm. broad in each 

 10 mm. in the proximal part of the arm, and (15) 18 brachials 1.1 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 69-77. 



Diodontometra bocki, arms 60 mm. long: (11) 12 brachials 1.3 mm. broad in each 

 10 mm. in the proximal part of the arm, and (14) 15 brachials 0.7 mm. broad hi the 

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

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



Antedon petasus, arms 75 mm. long: (12) 15 brachials 1.2 mm. broad in each 10 

 mm. 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. 



Poliometra 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. 



Pentametrocrinus 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 

 Comasterinae and Capillaster), Thalassometridae, Charitometridae, and Calome- 

 tridae, and in the Macro phreata ; while on the other hand indistinctly acute to right 

 angles of from 72 to 90 (average about 83) are found in the Comasterinae, Capil- 

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

 metridae), Tropiometridae, and Colobometridae. 



He said that from the figures given 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 of the 

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

 ever, the greatest number of segments 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 axis. 



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

 following give the size of 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 the pinnulate side. Figures omitted denote hypozygals. 



Comanthus japonica: IIBr 2 -80; IIIBr 2 -78; brachials 1-110; 2-87; 4-84; 

 5-90; 6-84; 7-80; 8-78; 9-76; 10-78: 11-78; after the twenty-third brachials 

 the angles are larger, up to 85 or 90. 



