CODIACEAE. 503 



The late Sir John Murray in reporting the results of the Challenger Ex- 

 pedition intimates that calcareous seaweeds and their broken down fragments 

 were the dominating elements in three out of four analyzed samples of so- 

 called ''coral" sand or mud from Bermuda and Dr. Henry B. Bigelow in a 

 paper on ''The Shoal-water Deposits of the Bermuda Banks" has named 

 Halimeda as a genus that has contributed an important part to the formation 

 of such sand or mud. If this determination is correct, it might be taken as 

 an indication of the existence of Halimeda Opuntia in Bermudian waters, for 

 the other species of the genus, both here and in the West Indies, would hardly 

 seem to occur in sufficient masses to be an important factor in the making of 

 sand and mud. 



Codium intertextum Collins & Hervey, forms spongy dark green, closely 

 adherent or repent, irregularly lobed or branched, mats or cushions under 

 shelving rocks or in rock crevices near the low-water mark, as at Gibbet 

 Island and Bailey's Bay. (Phyc. Bor.-Am. S018.) Also West Indian. 



Codium tomentosum (Huds.) Stackh. is not uncommon on rocks near 

 the low-tide line, forming spongy masses that are mostly from four inches to 

 two feet long. Its branches are cylindric or slightly flattened and repeatedly 

 dichotomous. 



Codium isthmocladum Vickers, is much like C. tomentosum, but is more 

 flaccid and more nitent when dry and its branches are often constricted at 

 their bases. Under a microscope, the utricles forming the superficial layer 

 are seen to be about twice as broad as those of C. tomentosum. (Phyc. Bor.- 

 Am. 1869, as Codium tomentosum.) 



Codium decorticatum (Woodw.) M. A. Howe (C elongatum Ag.) is per- 

 haps not always distinct from C. tomentosum but is usually recognizable by 

 being more elongate, more sparingly branched, by flattened expansions under 

 the dichotomies, and by the much larger utricles. Some remarkable specimens 

 collected in Tobacco Bay, St. George's, late in June were 2-4 feet long, with 

 flattened expansions A to 8 inches broad. (Phyc. Bor.-Am. 2017.) 



Family VAUCHERIACEAE. 

 Dichotomosiphon pusillus Collins, forms a dark green felt of slender inter- 

 tangled filaments on sand-covered rocks or in rock crevices near low-water 

 mark, as at Shelly Bay (Phyc. Bor.-Am. 2023) and on roots of mangroves, in 

 company with Bostrychia Montagnci. Under a compound microscope its 

 usually dichotomous or trichotomous filaments are seen to be constricted here 

 and there and there is nearly always a strong constriction at the base of each 

 branch. A complete constriction or an imperforate septum is, however, of a 

 very rare occurrence. The mode of reproduction has not been observed and 

 there is accordingly some doubt as to the generic and family affinities of the 

 plant. In its vegetative characters it shows resemblances to the Codiaceae. 

 The type locality is on the island of Jamaica. 



