LOWER CAMBRIAN. 43 
the frond, while in those genera the multiplication of the branches is by regular 
dichotomy or is four rayed as in Phyllograptus. 
Associated with these organisms are fragments of other organisms which have 
all the appearance of undoubted plant remains (described as Fucoides flexuosa by 
Emmons), and from the absence of characteristic graptolites in the shales it would 
seem to warrant the conclusion that these radiate specimens are not of graptolitic 
origin, but are referable to the sponges or possibly the marine alge. 
The name Dactyloidites bulbosus is proposed for these fossils. 
The material studied by Professor Hall, although abundant, was poorly 
preserved. Only a dark. stain remained on the slate, and of the original 
form nothing but the radiate arrangement of the lobes. The carbonaceous 
matter referred to is shown as a very thin coating in a few instances, but 
usually it is a dark coloration on the smooth surface of the slate. When 
subjected to a high degree of heat it is burned off and only a faint trace of 
the impression is left on the slate, as a slightly darker, smooth spot. The 
annelid trails and what may have been a simple form of alga often show 
more of the carbonaceous matter than the impressions of the meduse. It is 
probable that the mud contained more or less carbonaceous matter that was 
segregated in the annelid burrows and trails. The animal matter in the 
body of the medusze may have produced the trace now found on their 
impressions. The presence of the dark, carbonaceous matter is well shown 
in fig. 1 of Pl. XXIV, fig. 2 of Pl. XXV, figs. 1, 5, and 6 of Pl. XXVII, 
and fig. 5 of Pl. XXVIII. 
The reference of this fossil to the marine alge, by Dr. Fitch, was the 
most natural one to make in view of the form of the specimens and the 
presence of some carbonaceous matter. Professor Hall considered that the 
forms were referable to the sponges or, possibly, the marine algee. My first 
tentative opinion was that they suggested the impression of the mouth and 
gastric cavity of a species of medusa.’ Subsequent study of the fossil 
medusze of the Middle Cambrian led to the view that it was the body of a 
discomedusan, flattened in the slate, and not the cast of the interior. The 
reasons for this view are based on the direct comparison of a large series of 
specimens from the slate quarries at Middle Granville and the Middle Cam- 
brian forms from Alabama. Reference to this comparison is made in speak- 
ing of the relations of Brooksella and Laotira to other fossil medusze (p. 8). 
'Tenth Ann. Rept. U. 8. Geol. Survey, Part I, 1891, p. 606. 
