182 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Gloucester. The fronds form rose-colored crusts of considerable extent, and are so 

 closely adherent that they can scarcely be removed. The tetrasporic conceptacles are 

 large, but very much flattened. 



LITHOTHAMXIOX, Phil. 



(From 2,i$og, a stone, and d- fiviov, a bush.) 



Fronds calcareous, thick, at first horizontally expanded, but after- 

 wards producing erect knobs or coralloid branches; otherwise as in 

 Melobesia. 



A genus comprising probably not more than twenty or twenty-five good species, most 

 of which are tropical. The larger and more solid forms inhabit deep water. In Lilho- 

 thamnion the cortical portion is markedly developed, audit not rarely happens that 

 new lobes are produced which overlap the older ones and form an imperforate layer over 

 the older conceptacles, which are thus occluded before the spores are ripe. In such 

 cases sections show conceptacles which are apparently buried in the central part of the 

 frond. 



L. polymoephum, (L.) Aresch. (Milleporapolymorpha, L. ; Sp. Alg. — 

 Millepora (Nullipora) informis, Lamarck.— Melobesia polymorphs, Harvey, 

 Phyc. Brit., PI. 345.) 



Fronds thick and stony, purplish, becoming whitish, forming incrus- 

 tations of indefinite extent and occasionally rising in thick clumsy lobes, 

 punctate throughout with the very numerous, small, immersed concep- 

 tacles ; antkerozoids spherical, with an appendage at one end (Boruet) ; 

 tetraspores two-parted ; cystocarps ! 



On rocks and stones in deep pools and below low-water mark. 



Common from Nahant northward. 



Not known with certainty south of Cape Cod, but very common northward, where it 

 forms stony, purplish incrustations on rocks. As usually seen, it adheres closely to tho 

 rocks, covering patches of indefinite extent, and would be mistaken for a species of 

 Melobesia. It is so hard and adherent that it is mistaken by persons on the shore for 

 a part of the rock itself. Although the determination of the present species admits 

 scarcely a doubt, the form usually found with us is smoother and less lobed than 

 European specimens of the same species. In the description given above the tetra- 

 spores are said to be two-parted. This is true of all the American specimens examined, 

 but it may be that what we have seen were immature spores, which, when ripe, are 

 four-parted. 



L. fasciculatum, (Lamarck) Aresch. (Millepora fasciculata, Lam- 

 arck. — Melobesia fascieulata, Harv., Phyc. Brit., PI. 74.) 



Fronds purple, stony, attached, afterwards becoming free, very irregu- 

 lar in outline, densely branching, branches fastigiate, subcylindrical, 

 apices generally depressed; tetrasporic conceptacles densely covering 

 the branches, flattened, hemispherical ; tetraspores two-parted. 



On stones or in free globose tufts at low- water mark and in deep 

 water. 



Eastport, Maine; Europe. 



