PALJEONTOLOG V. 1 7 



Plate II. — Fig. 3 is a silicified specimen from Point Detour, 

 Lake Huron. 



LYELLIA DECIPIENS, N. Sp. 



Flat, undose expansions of laminated structure. Tubes one 

 millimeter wide, orifices not projecting, crenulated by twelve mar- 

 ginal crests. Diaphragms slightly convex. Interstitial spaces 

 usually larger than one tube diameter, their surface delicately 

 reticulated by circumscribed cell spaces, as in Heliolites, but in 

 vertical sections exhibiting a distinctly interlacing vesiculose struc- 

 ture, and not a tubular coenenchym. Found in the Niagara 

 group of Point Detour and Drummond's Island. Exteriorly it 

 fully resembles Heliolites interstinctus. 



Plate HI. — Fig. i represents a silicified specimen from Point De- 

 tour, Lake Huron. 



^LYELLIA PARVITUBA, N. Sp. 



Tubes one millimeter wide, with projecting orificial rims, radi- 

 ated within by prominent spinulose crests, and on the surface 

 of the interstices by the converging arrangement of the coenen- 

 chym vesicles. Interstitial spaces about equal to a tube di- 

 ameter, vesicles rather coarse. Diaphragms subplane, granulose. 

 Growth explanate, discoid, with a concentrically wrinkled epi- 

 theca on the lower side. Rarely found in the Niagara group of 

 Drummond's Island. In the Niagara group of Indiana and Ken- 

 tucky this species is very common, and is partly found silicified, 

 partly in calcified specimens with finely preserved structure. 



Plate II. — Fig. 4 is a calcified specimen from Louisville, Ky. 



Various other forms described by Billings under the name of 

 Heliolites are by structure true Lyellias, as Heliolites affinis, Bil- 

 lings ; Heliolites speciosus, Billings ; Heliolites exiguus, Billings : all 

 found at Anticosti Island. 



