(162) 



longer than broad. Substance rather fii'm, the older parts not adhering 

 very firmly to paper. Colour, a dark but rather dull reddish brown, not 

 changing much in drying. Favellse mostly binate, rovmdish, lateral on 

 the smaller ramuli, Tetraspores roundish, triparted, sessile on the upper 

 edge of the tooth-like processes. 



We have never met with this species on the east coast, and have not 

 seen Scotch specimens ; all ours are from the south of England, and are 

 of smaller size than ordinary. 



In habit it is somewhat intermediate between the last species and the 

 following, being much less bushy than the preceding, but less so than 

 C tetragomim ; it has also a close resemblance to G. brachiatum, but 

 from all may be distinguished by its microscopical characters. 



From the last species, C a7'hiscula, its much less dense ramification 

 will generally distinguish it ;] and from C. tetragonum the short, somewhat 

 clavate plumules, taper to the base, are perhaps the best mark of 

 distinction. 



It was first discovered on the north-east coast of Scotland, by Mr. 

 Brodie, of Brodie, and has since been observed on many other parts of 

 the British coast, but Professor Harvey informs us that he has not seen 

 any foreign specimens. In this country it does not seem to be uncom- 

 mon, gi'owing generally on the smaller Algse near low- water mark, or 

 beyond it, and occasionally in tide-pools at a less depth. 



EXPLANATION OF PLATE CXX. 



Fig. 1. — CaUithwnnion Brodkvi, natural size. 

 2. — Branchlet with tetraspores. 

 3.- — Same, more magnified. 

 4. — Branchlet with favellffi. 

 5. — Portion of stem. All mairnifiecl. 



