176 
then quickly becoming triangular, twice as broad as long, and in 
the terminal portion of the arm oblong, as long as broad. The 
first brachial has the middle of the distal edge for a short distance 
everted and spinous; this eversion rapidly increases in extent on 
the succeeding brachials until after the eighth or tenth the entire 
distal edge is produced and armed with fine spines. Syzygies occur 
between the third and fourth brachials, again usually between the 
ninth and tenth and fourteenth and fifteenth (the second often 
omitted) and distally at intervals of five to twenty-three oblique 
muscular articulations. On some arms the third syzygy may be 
as early as between the eleventh and twelfth, or it may be as late 
as between the twenty-fifth and twenty-sixth. 
P, absent; P, 10 mm. long, stiff and moderately stout, with 
twelve joints, the first two about as long as broad, the third slightly 
longer, becoming twice as long as broad on the sixth, but shorter 
again terminally; the last five joints have the distal ends armed 
with very prominent spines; P, 15 mm. long, stouter than P,, stiff 
and spine-like, with fifteen joints, the first two about as long as 
broad, the third slightly longer than broad, the following increasing 
in length, from the fifth onward being twice as long as broad or 
even longer, the låst four being short again; from the third onward 
the joints have projecting and very spinous distal ends, especially 
in the outer half of the pinnule; P, similar and of the same length; 
P, similar, 13 mm. long, but with only the last two joints small; 
P, similar to P,, and of the same length; P, slightly more slender 
than the preceding, but stiff and spine-like like them, 10 mm. long 
with fourteen joints resembling those in the preceding pinnule; 
next three or four pinnules similar to P,. but becoming very slightly 
more slender and increasing slightly in the number of joints; fol- 
lowing pinnules slightly longer with more numerous and propor- 
tionately shorter joints which in the proximal part have the ventro- 
lateral edges produced into thin rounded-triangular or wedge shaped 
processes, the apex being the anterior angle, which tend to separate 
off from the rest of the joint, thereby forming side plates; distally 
