1887.] NATURAL SCIENCES OF PHILADELPHIA. 269 



distributed at short and uuequal distances from each other. Inter- 

 nal structure composed of short, densely reticulated fibre, formed of 

 the skeleton spicules of the sponge, in bundles firmly united together 

 by colorless sarcode, which, together with the spicules, in a dried 

 state, simulates, from its hardness and vitreous appearance an en- 

 tirely silicified mass. Skeleton-spicule very robust, much curved, 

 cylindrical, rounded at both ends, smooth or microspined, about six 

 times longer than it is broad. Statoblast unknown." Carter. 



Log. "Rapids of the River Uruguay, above the town of Salto, 

 Uruguay." 



Several large specimens of this sponge have been collected by dif- 

 ferent travellers, and are deposited in English museums. Mr. Car- 

 ter mentions the names of Messrs. George Higgin, W. Bragge, 

 R. M. Andrew, and Dr. Garland in this connection. 



(VII b.) Gen. POTAMOLEPIS, Marshall. 

 Zeit. fur Naturwissenchaft, XVI. N. F.IX. Bd. 553. Leipzig, May, 1883. 



"Monactinellid, silicious, fresh-water spouges of great brittleness, 

 with curved, obtuse, smooth spicules, which, when dry, are closely 

 cemented together by a small quantity of organic substance. No 

 gemmules." Marshall. 



The descriptions of the following species, are abbreviated from a 

 translation of the above paper, as found in the "Ann. and Mag." etc. 

 1883, p. 391 etc. The specimens examined and described by Dr. 

 Wm. Marshall were collected by Dr. Pechuel-Loesche from the 

 Congo River, Africa, about 150 miles from the sea, and above sev- 

 eral "Falls" named. 



(1) Potamolepis leubnitziae, Marshall. 



"Forming crusts of 1-1"5 millim. thick, finely porous, of yellow- 

 ish white color and silky lustre ; exactly the appearance of unbaked 

 wafers. The surface presents a few crateriform elevations of 0"25- 

 0*40 mm. in height, standing in not very distinctly marked rows, 

 upon faint undulations, which divide dichotomously in both direc- 

 tions and frequently disappear, and in which a certain parallelism is 

 unmistakeable. At the summit of each elevation there is an oscu- 

 lum of irregular elongati-ovate and sometimes elongati-triangular or 

 pentagonal form, separated usually by a space of two millimeters. 

 The mouths, which are usually furnished not with smooth but with 

 finely notched margins, lead into shallow gastric spaces, Avhich im- 

 mediately break up into several canals ; in the angular mouths a ca- 

 nal is frequently found at each angle." "These canals run horizon- 



