1862.] DAWSON DEVONIAN PLANTS. 325 



appearance when deprived of their pinnules ; but the present speci- 

 mens are obviously of different character. In Prof. Hall's collections 

 from the Chemung group there are similar stems, with tubercles, but 

 with a minutely punctured surface. These may possibly indicate a 

 distinct species. 



{Algc^.) 



Among Prof. Hall's specimens are several which probably belong 

 to Algce ; but I regard them as too obscure in their affinities to 

 merit detailed description, with the exception of the following. 



68. IJpHANT^NiA Chemtjngensis, Yauuxem. PI. XYII. fig, 62. 



Vanuxem's * Report, Geol. New York,' p. 153, fig. 50. 



Fldbellate, invested, conical or hollow, cylindrical fronds, marked 

 eocternally with cross strice, dividing the surface into rectangular 

 spaces ; and in the cylindrical forms with rows of tubercles. 



Yanuxem has figured and described, under the above name, a 

 flabellate frond which he represents as apparently consisting of tape- 

 like bodies interwoven like basket-work. The specimens submitted 

 to me have, however, rather the character of a continuous surface 

 marked out into spaces by radiating and concentric striae. With 

 these fan-like forms are associated others that are bluntly conical, 

 and others still that are elongately conical or cylindrical ; and some of 

 the latter are covered with large tubercles arranged in vertical and 

 transverse rows, so as to give an appearance like that of stems of the 

 genus Halonia. One of these curious stem-like objects is illustrated 

 by fig. 62 (from a photograph). Some of the specimens are much 

 more finely marked than others, but there are gradations in this ; 

 and there are indications that some of the more finely marked stems 

 had flabellate or conical fronds upon them. These objects are very 

 perplexing, and are found in marine beds, but mixed with remains 

 of land-plants. On the whole I regard them as Algce with funnel- 

 shaped fronds sometimes prolonged into cylinders, and, when adult, 

 bearing fructification in tubercles on the sides of the cylinders. In 

 general form these plants may be compared with Algce of the family 

 DictyotecB ; but there is no indication that they resembled these in 

 details of structure. Some of the specimens have a slight carbonaceous 

 coating. The cylindiical forms seem to have been regarded by Conrad 

 as shells, and were named Hydroceras. The specimens in my pos- 

 session are from the Chemung group in New York and Ohio. They 

 may represent several species, but, on the other hand, it is quite 

 possible that they may be different states and portions of the same 

 plant. 



z2 



