42 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Eastport, Maine; Gloucester, Xahant, Mass. ; Northern Europe. Au- 

 tumn. 



This, by far the most striking of our Monostromata, grows luxuriantly in the large 

 tide-pool at Dog Island, Eastport, where it attains a length of oue foot. In habit it 

 resembles Ulva lactuca var. rigida, but it is of a deeper green. Our specimens were 

 collected in the month of September. As it occurs at Nahant the species is not gen- 

 erally more than two or three inches long, and recalls the figure of Ulva obscura, Kiitz., 

 Tab. Phyc, PI. 12, No. 2. It is found in the clefts of exposed rocks, late in the season. 

 Its color is a deep green when growing, which becomes brownish in drying. It does 

 not adhere well to paper. 



M. CREPIDINUM, n. sp. 



Fronds delicate, light green, one to three inches long, flabellately or- 

 biculate, split to the base, segments obovate, .018-36 mm thick, cells 

 roundish-angular, intercellular substance prominent. 



Government wharf, Wood's Holl, Mass. August. 



This small species is common on the piles of the wharf at Wood's Holl. It is very 

 soft, and collapses on removing it from the water. It preserves its color well on paper. 

 The above name is given provisionally, as we are not able to refer the species to any 

 known form. It resembles M. Wittrockii, Bornet, a species, we believe, not yet de- 

 scribed. Except in its small size, it is very near M. orbieulatum, Thur., but the thick- 

 ness of that species, as given by Wittrock, is .032-40 mm . An examination of a specimen 

 collected by Thuret, however, gives the same measurement as our species. If the 

 species eventually is united with M. orbieulatum, the present must be regarded as a 

 small form. 



ULVA, (L.) Le Jolis. 



(Supposed to be from ul, Celtic for water.) 



Fronds simple or branching, consisting of two layers of cells, which 

 are either in close contact with one another or else at maturity separate 

 so as to form a tubular frond. 



We have followed Le Jolis in uniting the old genera Ulva and Enteromorplia, and we 

 might perhaps have gone farther and united Monostroma with Ulva, for if Monostroma 

 Grevillei when young resembles an Enteromorplia, in its older stages it splits into 

 membranes consisting of a single layer of cells, which are certainly imbedded in a cer- 

 tain amount of gelatinous substance, yet so little as to make it doubtful whether to 

 call the frond parenchymatous or not. 



TJ. Lactuca, (Linn.) Le Jolis. ( Ulva Jatissima and rigida, Ag. & Auct. 

 recent. — TJ. latissima, Grev. & Harv. — Phycoseris gigantea, myriotrema, 

 australis, &c, Kiitz.) PL III. Fig. 1. 



Frond flat, thick, unbranched, variously more or less ovate in outline, 

 divided, the two layers of cells adherent. 



a. Var. kigida, (Ag.) Le Jolis. (TJ. rigida, Ag. — TJ. latissima, Harv., 

 Phyc. Brit., partim. — Phycoseris australis, Kiitz.) 



Frond rigid, rather thick, generally deeply divided, lacinise irregu- 

 larly lacerate-erose, the base of frond more dense and deeply colored 

 than the rest. 



