588 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [1885. 



59 miles SSW. from Fort Yuma, California, is a valuable additiou to 

 the spouge fauua of this continent, and interesting from the fact that 

 the typicalspecies, M. pliimosa of Carter, has heretofore only been found 

 in his original locality, the rock water-tanks of Bombay, East Indies. 

 That it should skip a whole hemisphere and only be found the second 

 time at its own antipodes is indeed remarkable. 



The lower reaches of the Colorado of the West extend for miles through 

 a region described by the collector as " the hottest, driest, and most 

 barren iu the United States," whose " vegetation consists of mesquit, 

 cacti, and the screw- bean, Stromhocarpiis puhescensy Its normal border 

 lands are known as the " tirst " and "second " •' bottoms," of which the 

 latter is the higher and of course more distant from the channel. By the 

 frequent changes in its bed, however, the river cuts through these, and, 

 washing away the one and filling up the other, reverses their physical 

 conditions. Upon the " second bottoms," then, said to be only reached 

 to any considerable depth by the annual tloods occurring during parts 

 of May and June, and not to continue flooded more than six weeks at a 

 time, the screw -bean abounds. It is described as a small tree of the 

 general appearance of a peach tree, but with more slender drooping 

 branches. More or less of an alkaline deposit whitens the ground upon 

 which they grow, and the a[)proaching traveler is puzzled to see in 

 strong contrast with it hundreds or even thousands of dark masses, 

 " like wasp's nests," suspended two or three feet above. 



It was this conundrum that confronted Dr. Palmer during his recent 

 visit, and the answer we have in the sponge before us. From the Ama- 

 zon Eiver in the tropics to the waters of Maine and i^ova Scotia in 

 the temperate regions of the north, sponges have long been known to 

 affect the pendent branches of stream-bordering bushes; but it is un- 

 likely that they have ever before been observed in such quantities sus- 

 pended for nine or ten mouths of the year over laud parched and deso- 

 late. 



On referring to the earlier descriptions of his discoveries by H. J. 

 Carter, Esq., F. E. S., we find that though he collected this species on 

 two or more occasions, the fragments were always found detached from 

 their place of growth and floating upon the surface in the water-tanks 

 referred to, about one month after the rainy season had commenced. 

 He believed that the vitality of the gemmules was preserved during the 

 dry season, notwithstanding their exposure to the sun and desiccating 

 winds, and that their germination after the water had again reached 

 them was followed by a very rapid growth of new sponge. This would 

 seem to have been the case also with the present variety, as, accord- 

 ing to the reports of tiie collector, the masses could not have been sub- 

 merged for a greater i)eriod than six weeks in any one year. Whether 

 the whole bulk as now seen was attained during a single season, or is the 

 cumulative result of several annual growths of the persistent masses, 

 cannot now be determined. 



