FIFTH REPORT OF THE DIRECTOR 1908 201 



are the separate joints of this form fill the otherwise fine grained 

 limestone containing the type specimens. It is therefore obvious 

 that accumulations of these joints are competent to form a pecu- 

 liarly granular limestone that may at times appear to be made up of 

 comminuted crinoidal fragments and again as of undistinctly 

 oolitic structure. The writer has collected a specimen of limestone 

 at Glens Falls that entirely consists of just such granules which in 

 a few places still retain their original serial arrangement and which, 

 in spite of the obscuration of their structure by secondary processes, 

 quite certainly are derived from calcareous algae. Stolley has al- 

 ready pointed out that the Siphoneae attained not only a high 

 development in Siluric time but that they also grew in great abund- 

 ance and that they will be found to have formed many limestones 

 in that era. If Solenopora is a Coralline alga, then also that family 

 of algae must have contributed largely to the formation of our 

 Trenton limestone by the var. tre n tone n sis of Solenop- 

 ora com pacta. 



Callithamnopsis Whitfield 



Professor Whitfield has proposed this new genus of fossil algae 

 for a form before described by Professor Hall as Oldhamia 

 fruticosa from the Trenton limestone of Platteville, Wis. We 

 have before us a new species from the Trenton of New York 

 referable to this genus and will for this reason enter a little more 

 fully on the discussion of the structure of the better preserved 

 genotype, C . fruticosa. We insert here copies of some of 

 the original figures [text fig. 4-7] illustrating this type and also a 

 camera drawing [pi. 1, fig. 3] of ours of one of the types to show 

 more clearly some of the important features of the form. 



The concise original diagnosis of the genus is : " Frond artic- 

 ulate, branched, branches opposite in pairs, in whorls near the 

 upper end of the joints, and composed of single joints between 

 bifurcations." 



The camera drawing of the type specimen here reproduced 

 shows the following characters : A distinctly monopodial growth 

 of the thallus with a thick branch of uniform thickness. This re- 

 tains in some parts a thick carbonaceous test. Where the latter is 

 broken out, a distinct sharp median longitudinal line is seen on the 

 impression dividing the latter into two convex halves, the whole 

 giving the impression of being produced by the crushing of a 

 hollow stem. The apex of the branch is seen to be rounded and 

 sharply defined. In several parts of the main branch distinct 



