168 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



ODOXTHALIA, Lyngb. 



(From oSoi'c, a tooth, a?.c, the sea.) 



Fronds dark purple, plane, deeply distichously pinnatifid, with a 

 Tudimentary midrib, margin alteruatelj^ toothed, formed of oblong inter- 

 nal cells and small irregularly shaped cortical cells; tetraspores tripar- 

 tite, arranged in two rows in short, corymbose, stipitate, lanceolate 

 branclilets (stichidia), which are marginal and generally axillary j cys- 

 tocarps similarly placed, ovate, with a distinct carpostome and pyriform 

 spores borne on a basal i)lacenta. 



A small genus of seven or eight species, which are confined mainly to the colder 

 waters of the northern hemisphere. 0. dentata occurs in the North Atlantic, extend- 

 ing as far sonth as Halifax. Several other species inhabit the North Pacific, especially 

 the vicinity of Kamtschatka, one siiecies occurring as for south as Japan and another 

 in California. The species are dark and opaque, and the polysiphonous structure is 

 scarcely visible in the older parts of the fronds, but is clearly seen in young shoots, 

 especially in adventitious growths. 



O. DENTATA, Lyngb. ; Pbyc. Brit., PI. 34. 



Exs. — Alg. Am. Bor., Farlow, Anderson & Eaton, Xo. 5G. 



Fronds four to twelve inches long, quarter of an inch broad, decom- 

 poundly i)innate, branches oblong, deeply pinnatifid or bipinnatifid, 

 lacinite alternate, linear, sharply inciso dentate toward the truncated ex- 

 tremities ', tetrasporic and cystocari^ic brauchlets clustered, axillary. 



Halifax, K. S., and several localities on the Saint Lawrence Eiver. 



This species has not yet been found within our limits, but may be expected on the 

 Maine coast. It is easily recognized by its color and ramification, and does not adhere 

 to x>aper in drying. As a rule, American forms of this species are narrower than the 

 common British form, but they are not distinct, and at Halifax the common British 

 form was dredged by Professor Hyatt in abundance. The 0. furcaia of Reinsch, 

 Contiibutiones ad Algologiam et Fuugologiam, p. 58, PL 4*2 a, is apparently the com- 

 mon narrow form of the i^resent species. 



EHODOMELA, J. Ag. 



(From podeog, red, and /nelag, black.) 



Fronds dark red, filiform or subcom pressed, pinnately decompound, 

 branches fibform, not contracted at base, composed of a monosiphonous 

 axis surrounded by several siphons and a thick cortex of small, irregu- 

 larly placed, polygonal cells ; tetraspores tripartite, borne in the ultimate 

 branches ; cystocarps sessile or pedicellate, spores pyriform, on short 

 stalks from the basal placenta. 



A small genus of dark-colored alga^ confined to rather high latitudes in both hemi- 

 spheres. It is connected by the genus PajtipMa'a with rohjaixihonia. The polysiphonous 

 character of the frond is seen at the tip, aud in most species cross-sections of the stem 

 show a circle of large cells surrounding the axial cell and a thick cortical layer. When 

 young the species are covered with dichotomous hairs. The genus is distinguished 

 at sight from Choudriopsis by not having branchlets constricted at the base. 



