112 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



cm. broad and 4 cm. thick. In some cases the organism has given rise to 

 oolitic spherules, which in radial section exhibit the branched tubular cells 

 Spreading in fan-shaped groups from the centre of the oolitic grain. The 

 section parallel to the surface of a nodule presents the appearance of a number 

 of circular or elliptical tubes' cut across transversely or more or less obHquely. 

 The resemblance between the fossil and a specimen of the recent species 

 Zonatrichia calcivora Braun, is certainly very close, but it is very difficult, 

 in the absence of material exhibiting more detailed structure than is shown in 

 the specimens described by Bornemann. to decide with any certainty the true 

 position of the fossil. The figures do not enable us to recognize any trace 

 of cells in the radiating tubes. It is possible that we have in Zonatrichites 

 an example of a Cyanophyccous genus in which only the sheaths of the 

 filaments have been preserved. In any case it is probable that this Mesozoic 

 species affords another instance of a fossil alga which has been responsible for 

 certain oolitic or other structures in limestone rocks. 



• I refer to Zonatrichites as in external form and section it closely 

 resembles CoUeiiia. 



Dr. A. C. Peale, in describing tbe limestones of the lower part 

 of the Algonkian section as exposed at the south end of the Madison 

 Range, Montana, on the south side of the Gallatin \'alley, mentions 

 the occurrence of so-called concretions that had been mistaken for 

 fossil turtles by the people living in the region.^ He describes the 

 concretions as very large, often measuring several feet in diameter 

 and from 6 to 12 inches (15 to 30 cm.) in thickness, averaging about 

 6 inches to a foot in diameter, with a thickness of only 3 to 4 inches 

 (7.5 to 10 cm.). 



The above description strongly suggests that the so-called con- 

 cretions are a form of Collcnia, or possibly Cryptocoon. It is antici- 

 pated that the locality will be visited, and study made of their 

 occurrence and character, during the season of 1914 (pp. 116-117). 



COLLENIA COMPACTA, new species 

 Plate 15, fig. 7 



This species has a turbinate growth, also in the solid layers of 

 limestone a massive, laminated growth that is irregular and com- 

 pact. The two forms of growth are well shown by plate 15, figure 

 7. The finer lainellse occur in bands outlined by coarser lamellae. 



Where the specimens in the collection were found they occurred 

 in a layer 9 cm. thick. The layer appeared to be made up of the 

 turbinate forms and intervening laminations and broken fragments. 



Bull. U. S. Geol. Survey, No. no, 1893, P- I7- 



