Miscellan eous. 



171 



Skeleton-spicules straight or slightly curved, mainly cylindrical, 

 but gradually sharp-pointed, sparsely microspined. 



Dermal spicules irregularly stellate, as in the typical species, but 

 in the specimens examined much fewer in number. They vary from 

 simple acerates with one or more long divergent branches to beautiful 

 radiate spherical bodies whose rays are nearly equal, spined, and 

 capitate by reason of recurved spines at their extremities. Another 

 form of spicule, probably also dermal, of which several ai'e seen upon 

 nearly every slide prepared for microscopic examination, is very 

 difficult of description. It may be said to be composed of an irre- 

 gular series of smooth curved rays arising from a nearly common 

 centre, and is somewhat suggestive of a hedgehog or Scotch terrier. 

 Birotulate spicules pertaining to the gemmulse, in length about 

 three times the diameter of the supported rotules ; shafts cylindrical, 

 plentifully spined ; spines 

 long, conical. Outer sur- 

 face of rotules convex, mar- 

 gins laciuulate ; ends of 

 incomplete rays obtuse, re- 

 curved. 



Sponge-masses subsphe- 

 rical, reaching 5 or 6 inches 

 in diameter. 



The woodcut represents : 

 a, skeleton-spicules ; b, c, 

 0, birotulate spicules of the 

 gemmule ; d, d, ends or 

 rotules of the same ; e, e, e, 

 f, dermal spicules ; g, y, 

 abnormal forms frequently 

 observed. The spicules are 

 magnified 200 diameters. 



This sponge, collected by 

 Dr. Edward Palmer along the banks of the Colorado River, near 

 Lerdo, Sonora, in North-western Mexico, about 59 miles S.S.W. from 

 Fort Yuma, California, is a valuable addition to the sponge fauna of 

 this continent, and interesting from the fact that the typical species, 

 M. plumosa of Carter, has heretofore only been found in his original 

 locality, the rock water-tank^ 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 in the United States," whose " vegetation consists 

 of mesquit, cacti, and the screw-bean, Stromhocarpus puhescens.'" 

 Its normal border-lands are known as the " first " 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, how- 

 ever, the river cuts through these, and, washing away the one and 

 filling up the otlier, reverses their physical conditions. Upon the 



