EXPLANATION OF PLATES. 189 



PLATE III. 



DiCTYOPHYTON TUBEROSUM. 



•^ Fig 1. A figure of a specimen of this species, natural size. This figure is ft'om a cast 

 of the original specimen described by Mr. Conrad. 



BiCTYOPHYTON NODOSUM. 

 '' Fig. 2. A figure from a cast made in a natural mould in the shaly sandstone. 



DiCTYOPHYTON ANNULATUM. 



VFio. 3. The figure is made partially from a cast of the stem in shaly sandstone : na- 

 tural size. 



DiCTYOPHYTON FENESTRATUM. 



^FiQ. 4. A portion of the stem near the base. The lighter jjortion of the figure shows 

 the exterior markings; while the other parts show the impression made 

 upon the matrix by the interior markings, or the cast of the interior of the 

 stem. 

 This species is more robust than any of the New- York species, and the cancellating 

 striae are stronger. The form of the stem has apparently been nearly cylindrical, gently 

 enlarging from the base, and a little undulating on the margin as if slightly annulated. 

 The relations of this species are clearly with the strong stems which I have referred, 

 with hesitation, to D. newberryi (See Plate iv, f. 3). 

 The specimen is from the Chemung narrows, Chemung county, N.Y. 



