GEODIA OVIS. 



167 



I measured forty-nine cladomes of anaclades of this sponge and arranged 

 these measurements in a series according to the thickness of the cladomal end 

 of the rhabdome. Apart from a gap between thicknesses of 7-16 n this series 

 is fairly continuous. Although the gap between 7-16 /i could probably be filled if 

 the search were continued long enough, it nevertheless indicates that anaclades 

 of these dimensions are not nearly so numerous as larger and smaller ones, 

 so that small and large anaclades can, to a certain extent, be distinguished. 

 This distinction is, however, not nearly so clearly marked as in the other Pacific 

 geodine sponges which possess small as well as large anaclades. 



The small anatriaenes (Plate 42, figs. 3b, 10, 11, 23b, 24b, 25-27) have a 

 rhabdome 670 fi-2.5 mm. long and, at the cladome, 2-7 // thick. In some of 

 these spicules (Plate 42, fig. 3b) the rhabdome is nearly cylindrical and rounded 

 at the acladomal end. In others (Plate 42, fig. 25) it is distinctly spindle 

 shaped, thickest in the middle, and attenuated towards both the cladomal and 

 the acladomal ends, the former being less than half as thick as the thickest, 

 central part of the rhabdome, and the latter pointed. The clades are slightly 

 curved, concave to the rhabdome. They arise either terminally (Plate 42, figs. 

 3b, 10, 23b, 25-27) or a little below the end of the rhabdome. In the latter 

 case a more (Plate 42, fig. 11) or less (Plate 42, fig. 24b) clearly pronounced 

 protuberance arises from the apex of the cladome. The chords of the clades of 

 these spicules are 6-43 /j. long and enclose angles of 41-65° with the axis of the 

 rhabdome. 



The large anatriaenes (Plate 42, figs. 28-40) have a rhabdome up to 23 mm. 

 long, which is, at the cladome, 17-45 /( thick. The clades are usually equal in 

 size. They arise nearly terminally, and there is only a slight protuberance on 

 the apex of the cladome. The clades are conic, pointed or somewhat blunt, and 

 curved, concave to the rhabdome. This curvature decreases distally, the ends 

 of the clades usually being nearly straight. An abrupt bend is sometimes ob- 

 served at the point where the more strongly curved basal part passes into the 

 nearly straight distal part (Plate 42, figs. 31, 39). The chords of the clades are 

 70-205 n long and enclose angles of 36-55°, on an average 42.5°, with the axis 

 of the rhabdome. 



Although the different kinds of euasters are connected by transitional forms 

 to a much greater extent than in most of the other geodine sponges, three kinds 

 can be fairly well distinguished. These are: 1. Large asters without centrum 

 and with slender, conic, pointed rays, in which the length of the rays is more 

 than five times as great as their basal thickness. These asters are here described 



