1887.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 359 



but dividing more rapidly and forming denser clumps, not unlike some 

 of the more open ones of fiircata, excepting for the larger size of 

 the branches. Branching occurs at intervals of about 10 to 30""", but 

 is often less frequent and the angle of divergence is generally less than 

 in the Stock Island specimens, due to the more numerous and closer 

 branches. In some specimens the tips of nearly all the terminal branch- 

 lets are more or less enlarged and furcate or digitate as in fnrcata. The 

 largest specimen measures 20'='" in height and 25°'" in width. The cells 

 are generally circular and may reach a diameter of 2.5'"™. Depth of 

 water 1 foot at low tide. A single specimen froni the Tortugas cannot 

 be distinguished from this variety. 



Dry Tortugas. — A large series of sjiecimens from the Tortugas ex- 

 liibits a very wide range of variation, tending in one direction towards the 

 Bermuda specimens described below. The clumps are generally dense, 

 sometimes very close in texture, the lower branches often much enlarged 

 and the basal portion frequently nearly solid. Branches divergent or 

 more or less i)arallel and vertical, dividing either rapidly or distantly, 

 occasionally coalescing, and thus forming clumps that vary greatly in 

 character and proportions ; sometimes low, convex, or hemispherical, at 

 others tall, enlarging upward. One tall clump consisting of stoat, as- 

 cending, closely-placed branches measures about oO''"', both in height 

 and spread (Plate XVIII, fig 2). Some of the specimens resemble those 

 from Eodriguez Creek both in the mode of branching and in the char- 

 acter of the tips of the terminal branchlets, but such clumps are gen- 

 erally lower and denser at the Tortugas. The main branches range in 

 diameter from 15 to 25™™. Terminal branchlets large and rounded at 

 the tips, or more or less compressed, broadened and bifurcate, or tri- 

 furcate, sometimes rapidly tapering. The cells vary greatly in size and 

 character, and may be circular or much crowded and polygonal ; the 

 walls are rarely very thick. One specimen, measuring 13*^™ in width 

 and 4"" in height, consists of a small solid base from which arise seven 

 very stout, rapidly tapering, irregular, and more or less sinuose and 

 divergent trunks, separated below by very narrow interspaces. On 

 the upper side these trunks give off from two to six short, stout, rounded, 

 simple branches or lobes, from 12 to 24™™ in length. 



Eastern Dry Bodes, 9 miles southwest of Key West (PI. XIX, fig. 1). — 

 The most exceptional forms in the collection are from this locality. They 

 are apparently stunted growths and form very dense convex clumps, 

 consisting of short, stout, very irregular, generally closely placed 

 branches, arising from a more or less solid base. The branches all 

 reach to about the same height, enlarge upward, and toward the sum- 

 mits are usually much divided, forming broad lobes, short, stout, simple 

 branchlets or mammillations. The largest clum{) measures 20^"' in di- 

 ameter and 12°™ in height ; the terminal lobes may have a spread of 

 20™™. The cells in all cases are deeply excavated, crowded, and with 

 thin walls; they vary in size, but measure on an average about 1.5™™ 



