96 ERYTHEA. 



the cells of G. polyrhiza, which is commou iu marine shells along 

 the coast. At the time the figures were drawn I had not succeeded 

 in finding any sporangia; since then I have found two; they were 

 of oval shape, narrowing at the base so as to seem somewhat stipi- 

 tate, about 100/i in length and 30// in diameter at the broadest 

 part. The sporangia of G. jiolyrhiza are variable in form, and 

 later observations may show that the sporangia are equally variable 

 in this case. In the absence of information as to their formation 

 and development the description is necessarily incomplete, but there 

 is no doubt of the distinctness of this species from G. polyrhiza. 

 The plant occurs only in small quantity, and is almost always 

 covered with a dense mass of Plectonema, so that it is very difficult 

 to examine. 



In addition to the species of perforating algse mentioned, the 

 shells contain also a very fine filamentous plant, which agrees well 

 with the description and figure of the fungus Ostracoblabe implexa 

 in the paper by Bornet and Flahault previously mentioned, p. 171, 

 pi. 12, figs. 1-4. 



The Plectonema is the only species occurring in sufficient quantity 

 to be noticeable to the naked eye; it gives a pale bluish green stain 

 to the shell; under the microscope it is of the same color, but 

 brighter. The tubes containing the Osti-acoblabe look pinkish 

 under the microscope, but the plant itself was found by Bornet and 

 Flahault to be quite colorless; Gomontia is grass-green and Hyella 

 pale brown; but neither is abundant enough to show externally. 



Besides the species in the substance of the shells, several algse 

 were growing on the outside; among them were Scytonema Mfoclirous 

 Ag., Dlchothrix Hosjordii (Wolle) Bornet, Microcoleus lacustris 

 (Rab.) Farlow, a sterile Bulbochsete and a young Nostoc; the two 

 latter not specifically determinable. Also on all the shells was a 

 Tolypothrix, fairly abundant, and apparently not hitherto described. 



Tolypothrix Setchellii. Filaments scattered or arranged in 

 parallel series and forming a layer, flexuous, 7 dm. long, 5-6,a 

 diam., occasionally thickened and subtorulose, repeatedly pseudo- 

 branched; branches patent; sheaths thick, gelatinous, refractive, 

 colorless or yellowish; trichomes pale serugineous, 4fj. thick, torulose. 



