128 



GEODIA AGASSIZII. 



either end (Plate 28, fig. 16c). The acladomal end usually thins out to a fine 

 point, it is rarely blunt. The rhabdomes of the anatriaenes of the young speci- 

 men from Station 4228 are at the cladome 18-27 ix (average maximum 25 fx) 

 thick. Among them a few with rhabdomes shortened and terminally thickened, 

 like the rhabdomes of some of the orthoplagiotriaenes, have been observed. 



The basal parts of the clades are curved, concave to the rhabdome, the 

 distal parts straight. Where the basal curved part passes into the distal straight 

 part, a slight, abrupt, angular bend is sometimes discernible (Plate 28, figs. 19, 20, 

 25). In most of the anatriaenes the distal straight part of the clade is about as 

 long as the proximal curved part (Plate 28, figs. 18-21, 24, 25); in some the 

 former is considerably longer than the latter (Plate 28, figs. 23, 26; Plate 32, figs. 

 43, 45, 46). Anatriaenes of this kind occur in the specimens from Stations 4199 

 and 4228. The chords of the clades of the anatriaenes of adult specimens en- 

 close with the axis of the rhabdome angles of 32-65°, on an average 45.8°. In 

 the anatriaenes of the specimens from Station 2886 this angle is considerably 

 larger than in those of the others. The three clades of the same cladome are 

 usually about equal in length (Plate 28, figs. 19-26). Sometimes, however, their 

 length is unequal (Plate 28, figs. 18, 27; Plate 32, fig. 45). In the adult specimen 

 from Station 3168 and in the young specimen from Station 4228 anatriaenes 

 with clades of unequal length are relatively more numerous than in the speci- 

 mens from the other stations. The chords of the clades of the anatriaenes of 

 the adult specimens are 40-155 n long, their average maximum length being 

 118.11 fj.. In the specimens from Station 2886 the clades of the anatriaenes 

 are very considerably shorter than any of the others. The chords of the 

 clades of the anatriaenes of the young specimen from Station 4228 are 60- 

 110 [.i (average maximum 95 fx) long and enclose angles of 31-45° (average 

 38°) with the axis of the rhabdome. In the immature specimen described 

 by Lambe the anatriaenes have a rhabdome 3.3-4.7 mm. by 22-28 fx, clades 

 45-100 IX long, and clade-angles of 41-52°. 



In the centrifugal spicule-preparations of this specimen also a few minute 

 dermal anaclades were observed. These have a rhabdome about 290 /x by 1-1.5 

 /X at the cladome and 3-5 jx at the thickest point below the middle; their clades 

 are 4-6 pt long; the clade-angles are 38-62°. These spicules may be foreign. 



