58 



Where best developed, the algae lie in zones parallel with 

 the bedding planes in the Salem limestone (Mississippian) in 

 which they occur, and their constituent material is essentially 

 like that of the surrounding limestone, both in composition and 

 in structure. 



Type Locality. — The genotype, as well as the type specimen 

 of my new species, Glohulinea giganteus Ulke, n. sp., can be 

 seen exposed on the weathered top face of the 2nd lowest step, 

 a block of Salem limestone cut about 10 feet long, 1-foot tread 

 and 7-inch rise, in front of the 16th Street entrance of the Bap- 

 tist Memorial Church at 16th Street and Columbia Road, 

 Washington, D. C. The type specimen is the stout, reversed 

 U-shaped alga, approximately 30 in. long and .75 in. diameter, 

 appearing in the right half of a 3-foot section on the left hand 

 portion of the stone block. It is illustrated in Fig. 1, as a, b, c, 

 grouped with portions of other algae of the same species and in 

 Fig. 6. 



Classification and Occurrence. — These fossil algae probably 

 belong to the class Chlorophyceae, order Siphonales and family 

 Siphoneae, and represent completely calcified rope-like remains 



EXPLANATION OF PLATE 



Fig. 1. Sketch of groups of fossil algae visible on the weathered, flat, top 

 face of the next to lowest step, a block of Salem limestone, in 

 front of the 16th Street entrance of the Baptist Memorial Church 

 of Washington, D.C. Portion of step illustrated is a 3 ft. long sec- 

 tion at left end. The alga a, b, c shown in Fig. 1, approximately 

 30 in. long and .75 in. diameter, is the genotype of GLOBULINEA 

 n. gen. Ulke, and specific type of G. gigantea, Ulke, n. sp. 



Fig. 2. Sketch of a long and slender "rope and bead-like" alga (a to g) of 

 a variety which I have named Glohulinea gigantea var. catenae- 

 formis, visible on the top slab of Salem limestone of the wall 

 on 16th street, between Allison and Buchanan, in Wash. D.C, 

 the particular stone being the 7th, S. of the main entrance to 

 Crandall's residence. This variety differs from the above type 

 species in being slender (3/16 to \ in diam), in usually lacking a 

 continuous stem sheath, and in its branching habit. Were it not 

 for the occurrence of somewhat intermediate forms, this variety, 

 catenaeformis, might well be considered a valid new species. 



Fig. 3. Sketch of an alga (a, b, c) with several short branches, on 5th 

 capstone, N. of Allison, on 16th street. 



Fig. 4. Sketch of a young branching alga, lacking septa, on 7th step, 38 

 in. fr. left end, front Columbia St. entrance, Bapt. Mem. Ch. 



Fig. 5. Algal stem, with possible fruiting body, on step shown in Fig. 1. 



