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University of California. 



[Vol. 1. 



and relationship. In a few instances the original hollow has been 

 in part filled with the stained matrix, so that the thickness of the 

 bounding walls is shown, and this is more particularly the case with 

 the conical forms of the genus Dictyomitra (PI. 14, Figs. 15, 16, 17) 

 in which the basal portion was open. In the spined forms the 

 spines appear as projecting transparent rays extending from the 

 clear central mass. Rarely indeed are traces of the characteristic 

 lattice structure of the radiolarian test preserved, but occasionally 

 it is shown by the rounded dots of the red matrix on the surface of 

 the cast, in which also the original regular arrangement of the holes 

 in the test can be recognized (Fig. 7). 



In the light-colored Buri-buri rock there is but little difference 

 in the appearance of the silica filling the radiolarian casts and that 

 of the matrix, consequently they can only be faintly distinguished 

 in thin sections, but usually the silica of the cast is free from the 

 minute granular particles which abound in that of the matrix. Fre- 

 quently, however, in this rock the radiolaria have been infilled with 

 a light brownish silica, which allows the wall of the test to be dis- 

 tinguished, but the details of the structure have been obliterated 

 just as much in this light-tinted rock as in the red rock from Angel 

 Island. 



The unfavorable state of preservation of these radiolaria makes a 

 specific determination almost out of the question, and even the gen- 

 era to which they belong cannot, as regards most of them, be pos- 

 itively recognized. The majority of them evidently belong to sim- 

 ple spheroidal and ellipsoidal forms, included in Haeckel's suborders 

 Sphaeroidea and Prunoidea, and they range in size from .055 to .3 

 mm in diameter. The spherical forms may be included in the 

 genus Cenosphcera, Ehrenberg (Figs. I, 2 and 3), and Carposphcera, 

 Hseckel ; in this latter there is an inner medullary shell (Fig. 4}. 

 The ellipsoidal forms with smooth contours (Figs. 5,6, 7) probably 

 belong to Cenellipsis, Haeckel; they are very abundant; those 

 forms, with numerous radial spines on the surface (Figs. 8, 9), come 

 into the genus Eliipsidium, Haeckel; and those with a single 

 extended spine or ray at one pole (Figs. 10, 11) into Lithapium, 

 Haeckel. There are further some peculiar types which may pro- 

 visionally be placed in the suborder, Discordea, Haeckel. In one 



