26S BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



The second brachials vary from slightly to considerably larger than the first, ir- 

 regularly quadrate in fonn, with the middle of the proximal border more or less depressed 

 into an obtuse angle entering the concavity on the distal border of the first. 



The first syzygial pair is oblong, from as long as broad to almost twice as broad as 

 long, or much longer interiorly than exteriorly, with the hjT30zygal (third brachial) 

 wedge-shaped or triangular and the epizygal oblong. 



The following bracliials are oblong or slightly wedge-shaped, from about as long as 

 broad to half again as long as broad, after the eighth to twelfth becoming very obliquely 

 wedge-shaped or triangular, about as long as, or rather longer than, broad, and distally 

 less and less obliquely wedge-shaped and terminally oblong and elongate. 



In Thysanometra tenelloides the shape of the brachials is quite unique, recalling that 

 of the brachials in Amphimetra. Tliose following the first syzygial pair are wedge- 

 shaped, about twice as broad as long, gradually becoming more and more nearly oblong, 

 and at length quite oblong, not quite twice as broad as long, after about the end of the 

 proxinud third of the arm. Distally the brachials gradually become more elongate, at 

 the end of the arm being twice as long as broad or even slightly longer. 



Syzygies occur between brachials 3+4, 9 + 10 and 14 + 15, and distally at intervals 

 of from 2 to 6 (usually 2 or 3) muscular articulations. 



In Coccometra nigrolineata the edges of the elements of the IBr series and of the 

 lower brachials arc everted, prominent, and very spiny; in O. hageni 2 or 3 of the bra- 

 chials following the second S3'zygial pair have a group of small spines in the central portion 

 of the distal end. In the other species the ends of the brachials are quite smooth. 



A curious feature in this group is the occurrence of characteristic and definite 

 black markings on two species. In Coccometra nigrolineata there is a conspicuous 

 median line of black on the IBr series and the lower portion of the arms bej'ond which 

 each syzygial pair bears a transverse black band or large black spot. In C. guttata 

 there is a large black spot on either side of each syzygial pair, and the inner half of the 

 articular faces of the sj'zygies is also black. There are no black markings in any of 

 the other species known. 



The oral pinnules show little diversity. Pj is composed of 31 to 40 segments of 

 which at least those in the proximal half are barely, if at all, longer than broad. The 

 pinnule is slender and highly flexible, the corners of the short segments being truncated, 

 though sometimes more or less swollen dorsall3^ 



P2 maj"- be longer than ?,, but is usually somewhat shorter and may be not much 

 more than half as long. It is stouter and stifi"er than Pj and is composed of 12 to 20 

 segments, of which the first 2 or 3 are about as long as broad and those following become 

 elongated. It may bear a gonad. The following pinnules resemble Pj. 



The distal pinnules are slender with much elongated segments, longer or shorter 

 than P,. 



The deposits along the sides of the ambulacra! grooves of the pinnules in Cocco- 

 metra consist of long slender uniform rods, straight or slightly bent in the middle, 

 and pointed at each end or slightly roughened at the distal end. In Thysanometra 

 there is a, narrow but very conspicuous calcareous band 2 or 3 meshes wide, rarely 

 wider, which runs from the borders of the pinnulars into each of the ambulacral lappets, 

 where, toward the inner edge, it gradually broadens and forks so that its end is Y- 

 shaped, the pro.xunal arm of the Y being as broad as the original band and making 



