PAL^ONTOLOG V. T O I 



than the interstitial cell spaces of the peripheral area. Associated 

 with the specimens exhibiting plainly the carinated character of the 

 lamellae, others entirely similar to them are found with veiy obscure 

 carinations. The calyces of the largest specimens attain a diameter 

 of about six centimeters. The average number of lamellze, in the 

 circumference of calyces four centimeters wide, is from seventy-five 

 to eighty-five. The external mode of growth is subject to a great 

 many variations, from the short, broadly turbinate cell to long, cylin- 

 drical stems, with all sorts of irregularities by constrictions, flex- 

 ions, etc. Occurs in the upper Helderberg group, and in the 

 Hamilton group of Michigan, Canada, New York, Ohio, and in the 

 Western States. The specimens of different localities and of differ- 

 ent strata show some differences, but not in a degree to justify 

 their separation into several species. 



Plate XXXV., Upper tier. — The three left-hand figures are 

 medium-sized specimens, found in the Hamilton group of Widder, 

 C. W. ; the two outer calyces are short, turbinate ; the adjoining 

 specimen exhibits an irregularly distorted cylindrical growth. 

 The third upper figure from the left is found in the Hamilton 

 group of Thunder Bay ; the lamellae on one side of the calyx are 

 plainly carinated, while on the other side scarcely any traces of 

 carination can be observed. 



CYATHOPHYLLUM JUVENIS, N. Sp. 



A very constant form found in association with the preceding 

 species, resembling it in all particulars, but in all proportions 

 smaller. The arched carinse are closely approximated, twenty-four 

 on the space of a centimeter. Number of lamellae from sixty to 

 seventy in the circumference of calyces two and one quarter centi- 

 meters wide, which is about the largest size observed. Found in 

 the Hamilton group of Thunder Bay, Little Traverse Bay, at Wid- 

 der, C. W. ; also in the upper Helderberg strata of New York, 

 Ohio, Kentucky, etc. 



Plate ^XXXV., Upper tier. — The three smaller specimens on 

 the right side of the plate ; the longer cylindrical specimen is of 

 larger size than usual. 



