176 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



apposed faces of the two portions of a syzygial union are marked by a series of 

 slightly elevated ridges with alternating furrows which radiate from the opening 

 of the central canal toward the dorsal margin of the joint face, in Comaster 

 novceguineoi these ridges are frequently not perfectly continuous but are broken 

 up into a row of little elevations, squarish or oblong in shape, and arranged with 

 their longer axes radiating outward from the central canal; on some joint faces 

 these are not very numerous. 



In the species of Comaster other than the two mentioned the elements of all 

 the division series beyond the IBr series and the first two brachials of the free 

 undivided arms are always united by syzygy, and these syzygies range all the way 

 from an almost typical synarthry to a quite typical syzygy (part 1, fig. 40, p. 75) 

 With very rare e.xceptions, however, the median ridge between the central canal 

 and the middle of the dorsal border of the joint face is always more or less 

 developed. 



In the genus Comatula the synarthries between the elements of the IBr series, 

 the IBr series hvhen present), and the first two brachials are almost invariably 

 replaced by highly perfected syzygies (part 1, fig. 39, p. 75). But in the so-called 

 slender-armed variety of Comatula solans, C. pectinata, and G. purpurea, in 

 which the arms are not swollen basally, the synarthries are retained, though their 

 joint face sculpture is much less marked than usual (part 1, fig. 36, p. 75). 



In Comactinia, which is very closely related to Comatula, the synarthries 

 remain unmodified. 



In the so-called bourgueticrinoid (synarthrial) articulations between the 

 columnals in Bafhycrinus and in the very young pentacrinites (observed in 

 Isocrmus and in Comastrocnnus), there is a tendency for the median ridge to break 

 up into a number of smaller ridges which radiate outward from the central canal 

 so that a joint face is formed which is. to all intents and purposes, a syzygy. 

 This articulation, which is quite comparable to the proximal syzygy in the arms of 

 the comatulids, becomes in the pentacrinites the characteristic stem joint in which 

 the apposed faces of the columnals show complicated petaloid figures. 



In the brachial synarthrial articulations (figs. 1084, pi. 18; 1099, 1103, 1107, 

 pi. 19; 1123, 1127, 1131. 1135, pi. 21; and part 1, figs. 6, p. 63; 10, p. 65; and 30, 

 33, p. 71) the apposed joint faces are transversely oval and are divided in the 

 median dorsoventral line by a more or less broad ridge running from the dorsal 

 and ventral borders to the rim about the central canal, so that the two ligament 

 masses occupy each a large semicircular or semielliptical area on either side of 

 the dorsoventral line. 



With the brachial synarthries the articulations in the column of the larval 

 comatulids, which consist of two ligament masses, one on either side of a median 

 ridge coinciding with the longer axis of the joint face, as well as the similar 

 articulations between the cirrals and the pinnulars from the second outward, are 

 in all ways homologous (part 1, fig. 139, &, p. 205). 



