GEOL. VOL. I.] SMITH SANTA CATALINA ISLAND. 47 



forms relatively large. Sponge spicules are also present, 

 but I could not certainly distinguish any Radiolaria. No 

 Foraminifera to be seen in this specimen, and there was no 

 reaction of the rock in acid. It is not unlikely that the 

 calcareous organisms have been leached away, for minute 

 empty pores can be seen in transverse sections of the beds. 

 It has a lesser proportion of angular rock chips than the 

 preceding (No. 90). 



" No. 147. Very soft, earthy white rock, readily break- 

 ing up into fine flaky laminae. No reaction in acid. Like 

 the preceding this is also nearly entirely a diatomic rock, 

 but the diatoms are here of different forms, Melosira? and 

 Grammatophora being most conspicuous. There are fair 

 numbers of sponge spicules, usually broken; they are chiefly 

 pin-shaped and styliform. Neither Foraminifera nor Radio- 

 laria were recognizable in the material examined. The 

 angular rock chips were fewer in this rock than in the pre- 

 vious specimens (90 and 118). 



" No. I52. 1 A pale gray, hard rock just scratches with 

 knife compact, flinty fracture, readily effervesces in acid. 

 Examined in section only. It consists, like the soft rock 

 above referred to (No. 90), mainly of diatoms and diatomic 

 debris; the ground-mass of the rock is, as far as can be seen 

 under the microscope, wholly of the broken up diatom 

 frustules. Both the minute fragments and the entire forms 

 are as unchanged as in the soft rocks. Coscinodiscus is 

 abundant, also Navicula, Grammatophora and other forms. 

 Some of the spaces between the diatom frustules have been 

 infilled with calcite. There are a few Radiolaria present, 

 spheroidal and discoidal forms, but their numbers are insig- 

 nificant in comparison with the diatoms. Sponge spicules 

 are apparently absent. Foraminifera are fairly common and 

 well preserved, showing their wall structures; the most 

 abundant is a large species of Textularia, probably the same 

 form as that in No. 90. The interiors of the Foraminifera 

 have been infilled with calcite. Angular chips hardly to be 

 seen in the sections of this rock. 



1 No. 152 is the limestone, the analysis of which is given later, p. 50. 



