264 PROCEEDINGS OF THE ACADEMY OF [1887. 



somewhat resembling tentacles. Spicula birotulate, long, very deli- 

 cate ; length of axle 0"0015 inches, one or more large spines on each 

 axle. Rotulse slightly arcuate, equal in size. Length of tube to 

 foramen 0"01 inches. Length of tentacle shaped processes, one 

 fiftieth to one eightieth of an inch." 



(3) Carterius latitenta. Potts. Proc. Aead. Nat. Sei. Phila. .July ISSl, p. 176. 

 (PI. VI, fig. V,. PI. XII, fig. V.) 



Sponge green, encrusting stones etc.; texture very loose ; the 

 longer bands of skeleton spicules rising into abrupt wave-lines at 

 short distances ; masses thicker near the middle. 



Gemmulse numerous, spherical ; crust charged with birotulate 

 spicules ; foramina prolonged into tapering (narrowing) tubules 

 shorter than those of C. tubisperma ; terminations rounded. Cir- 

 rous appendages, at first flat and ribbon-like, enveloping the tu- 

 bule, (or pierced by it), some distance below its termination ; fre- 

 quently but one, rarely more than two of these, which soon become 

 slender and rounded, long and tapering, occasionally subdividing 

 into many short irregular ones. (PI. VI, fig. v. a. and d.) 



Skeleton spicules fusiform, smooth or very sparsely microspined, 

 gradually pointed. (PI. XII, fig. v. a.a.) 



Dermal spicules long, acerate, slightly curved, entirely spiued ; 

 spines irregular, longer towards the middle of the spicule. (Ibid, 

 c.c.) 



Birotulate sjiicules stout ; shafts with numerous long, pointed 

 spines ; surfaces of rotules rounded ; rays deeply cut, tapering, some- 

 times incurved (ibid, b.b.b.d.) (PI. VI, fig. v. b.) 



Meas. Skeleton spicules O'Olll by 0"00045 inches. Length of 

 dermal spicules 0-0038 inches. Birotulates 0-0019 by 0-00015 in- 

 ches. Diameter of disk O'OOl inches. 



Hab. On stones etc., in rapidly running water. 



Loc. Chester Creek, Pennsylvania ; Western New York etc. 



In the summer of 1881, I resided temporarily in a fine agricul- 

 tural district in Chester County, Pennsylvania. As a rule, July is, 

 in this part of the world, too early for the collection of mature spec- 

 imens. Some species, however, form their gemmules thus early ; 

 and, while wading along the east branch of Chester Creek, there a 

 shallow stream, averaging eight or ten feet in width, turning over 

 stones in the "riffs," or little rapids, probing the roots of encroach- 

 ing trees and examining the stems of water plants, I found traces of a 

 sponge, which, under the microscope, proved to be a third species of 



