502 CODIACEAE. 



cortex of the stalk, which, under a hand lens, appears spongiose or velutinous- 

 tomentulose, while that of P. capitatus is compact, indurated, and smooth. 

 Under higher magnification, the ultimate branchlets of the corticating fila- 

 ments are seen to be elongate and taper-pointed, while in P. capitatus, they 

 are short-oblong, obtuse, truncate, or capitate. P. pyriformis has its best 

 development in the Bahamas, but it has been found in Ely 's Harbor and 

 Harris Bay and doubtless occurs elsewhere in the Bermudas. (Phye. Bor.- 

 Am. 2075.) 



Halimeda Tuna (Ell. & Soland.) Lamour. occurs on rocks in shallow 

 water, as at Spanish Point, Gibbet Island, inlet of Harrington Sound, Achilles 

 Bay, etc. In this, as in all the Halimedas, the thallus is calcified and jointed. 

 In H. Tuna, the segments are discoid, mostly reniform or semi-orbicular. The 

 filaments of the central strand fuse in twos or threes at the nodes but are 

 otherwise commonly free. (Phyc. Bor.-Am. 1918.) 



Halimeda tridens (Ell. & Soland.) Lamour. grows usually on a sandy or 

 muddy bottom and in 1-100 feet of water. It is more shrubby in its habit 

 than H. Tuna and the segments are typically flattened and 3-lobed or 3- 

 dentate, though variable as to this character, as also in the shape of the seg- 

 ments, which range from subquadrate-orbicular, with the long axis transverse, 

 to obovate, deltoid-obovate, cuneiform, or occasionally subcylindric. When 

 decalcified the cells of the cortex are found to measure 49-77 M in average 

 maximum diameter in surface view. 



Halimeda Monile (Ell. & Soland.) Lamour. differs from H. tridens chiefly 

 in having its segments mostly subcylindric and in having its surface cells only 

 30-44 fj. in average maximum diameter. (Phyc. Bor.-Am. 1915; also 1917 as 

 H. tridens in the one copy examined.) 



Halimeda simulans M. A. Howe, imitates H. Tuna in its discoid usually 

 subentire or crenate segments, but it is really more akin to H. tridens and 

 H. Monile, as is shown by the fact that the filaments of the central strand, as 

 in these two, form a single coherent inter-communicating mass at each node. 

 The surface cells are small, as in H. Monile. H. simulans has recently been 

 found near Tucker's Town by Hervey. (Phyc. Bor.-Am. 1916.) 



Halimeda Opuntia (L.) Lamour. This species was reported from Ber- 

 muda by Kein, but we have seen no Bermudian specimens. It is, however, very 

 common in the Bahamas, southern Florida, and the West Indies, and its exist- 

 ence in the Bermudas is not improbable. It often occurs in rather deep 

 water (10-100 ft.) and may be brought to light in Bermuda by dredging 

 operations. It differs from the other species in forming large tangled mats or 

 cushions. It is strongly calcified, and the discoid segments are clearly or ob- 

 scurely nerved. The branches and their segments are very often turned or 

 twisted at various angles, and in its more luxuriant development its branches 

 form long tangled chains. Certain naturalists claim to have experienced a 

 prickling sensation as of a slight electric shock when handling plants of this 

 species, either with bare hands or with metal implements. 



