GEODIA BREVIANA. 



159 



triaenes but with longer clades (up to 110 long) and smaller clade-angles (about 

 45°) were also observed. 



The minute dermal anaclades (Plate 36, figs. 1-9) are triaene, diaene, or 

 monaene. The triaene forms are more numerous than the other two. Their 

 rhabdomes are usually quite strongly and somewhat irregularly curved (Plate 

 36, figs. 2, 4, 6, 8), thickest about two thirds of their length from the cladome, 

 and rounded at the acladomal end. They are 480-560 // long and at the cladome 

 2.5-4.5 thick. At their thickest point they are about twice as thick as at 

 the cladome and here measure 5-8.6 /j. in transverse diameter. The rounded 

 acladomal end is 3.4-7 // thick, slightly thicker than the cladomal end. The 

 clades are conical and usually pointed and uniformly curved, concave to the 

 rhabdome. In the triaene forms (Plate 36, figs. 1-5) the chords of the clades 

 are 7-9 fi long and enclose angles of 48-58° with the axis of the rhabdome ; in the 

 diaene and monaene forms (Plate 36, figs. 6 9) the chords of the clades are 11- 

 12 n long and enclose angles of 42-46° with the axis of the rhabdome. In young 

 forms like the left one of the two represented in Plate 36, fig. 1, the clade-angles 

 are larger. In the specimen described by Lambe the minute dermal anaclades 

 (not mentioned by Lambe, 1893) are exceedingly abundant. Their rhabdome 

 is 350-610 by 1-3.5 fx at the cladome, and 5-7 /j. at the thickest point below 

 the middle; the clades are 2-12 long, the clade-angles 42-60°. Some of the 

 minute anaclades of this specimen have a straight, conic, apical ray, an 

 epirhabd, 5-8 // long, and therefore appear as mesanaclades. 



The thick-rayed oxyasters (Plate 35, figs. 18a, 19a, 22a, 24, 27) have five to 

 twelve rays and a small centrum, the diameter of which is from two to three 

 times as great as the basal thickness of the rays. The rays are usually simple, 

 radial, and regularly distributed. Occasionally irregularities are observed due 

 either to an irregular position or to a bifurcation of one or more of the rays. 

 The two branches of the bifurcate rays are nearly parallel and lie close together. 

 The ra3's are straight and conical, pointed, or blunt. Th^ir proximal part is 

 smooth, their distal part covered with rather large spines. The spines are not 

 very numerous and rise vertically from the rays. Their ends appear to be 

 curved backward towards the centre of the aster in a claw-shaped manner. The 

 rays are (without the centrum) 7.5- 11 /t long and 1-2.2 pt thick at the base, the 

 total diameter of the oxyaster being 16-26.5 A correlation (inverse propor- 

 tion) between the size and the ray-number is observed in so far as the oxyasters 

 with the most numerous (twelve) rays do not exceed 18.5 /t in total diameter. 

 In the specimen described by Lambe these asters have from five to nine rays 1.4- 



