OF ARTS AND SCIENCES. 375 



belong to the variety under consideration. I had named them P. pec- 

 tiaata, Ilarv. (P. densa, Ag.), after comparing them with a specimen 

 from Lenormand, which I have since found out is incorrectly named. 



The species of Ptilota of our west coast may be briefly eimmerated 

 as follows : — 



P. densa, Ag., in which the pinnce are falcate and incised on the 

 outer side only, as is well shown in PI. XXXII. B. fig. 2, of Nereis 

 Am.-Bor. This species seems more common southward. 



P. hijpnoides, liar/. ]\Iore delicate than the last, with pinnoe, which 

 are lanceolate, with a smooth, slightly crenulated, or dentate margin, 

 and contracted at the base. PI. XXXII. A. B. C. 



P. aspenioides, Ag., differing fi-om the last by being coarser and 

 having the usually somewhat serrated pinnae decurrent at the base. 

 This occurs in Oregon, and is a common species of Alaska. 



P. plumosa, Ag. More common northward, and var. filicina found 

 also in California. In this species the pinnae are regularly pectinate 

 on both sides. 



314. Ptilota asplenioides, Ag. Oregon northward. 



315. Ptilota plumosa, Ag.,aiid var. filicina. California north- 

 ward ; east coast, very rare ? 



olG. Ptilota serrata, KUtz. Nahant, Mass., northward, com- 

 mon ; S itch a. 



317. Ptilota elegans, Bonnem. New York northward. Not 

 so common north of Cape Cod as in Long Island Sound. 



318. Crouania attenuata, J. Ag. Key West. 



319. Halurus equisetifolius, Kiitz. 



320. Griffithsia corallina? Ag. and var. tenuis. — Under this, 

 in the Nereis Am.-Bor., are included two different species, neither of 

 which is certainly C coraUina. The variety tenuis was afterwards 

 considered by Harvey a Callithamnion. This variety occurs as far 

 north as Gloucester, Mass. In the absence of fruit, it is impossible to 

 say whether it is a Callithamnion or not. 



321. Callithamviox Pikeanum, Harv. California. 



322. Callithamnion tetragonum, Ag. New York northward. 



323. Callithamnion Baileyi, Harv. New York northward. 



324. Callithamnion squarrllosum, Harv. California. — The 

 specimens distributed under this name in Hall's Oregon Alg^e now 

 seem to me doubtful. 



32.5. Callithamnion Borreri, Ag. New York to New Bedford. 



326. C.\LLiTHAMNiON POLYSPERMUM, Ag. New York southward. 



327. Callithamnion byssoideum, Arn. New York to Nahant,, 

 Mass. 



