1887.] NATURAL SCIENCES OF PHILADELPHIA. 251 



(6) Tubella pennsylvanica, Potts. Proc. Acad. Nat. Sei. Phila. 1882, p. 14. (PI. 

 VI, fig. ii, PI. XII, figs, i, ii, iii.) 



Sponge gray ; or, when growing in the light, green ; minute, 

 incrusting ; surface of mature specimens often found covered with 

 parallel skeleton spicules, not yet arranged to form cell-like inter- 

 spaces. 



Gemmules very numerous, small ; granular crust thin or thick; 

 sometimes covering to a considerable depth, the outer extremities 

 of the rotules, which in other cases project beyond it. (PI. VI. 

 fig. ii.) 



Skeleton spicules extremely variable as to length and curvature; 

 sub-fusiform, acuminate or rounded ; entirely sjiined ; spines large, 

 conical ; terminations mostly rounded. (PL XII, fig. i, ii and iii, 

 a.a.a.) 



Dermal spicules wanting. 



Birotulate spicules surrounding the gemmules numerous, consisting 

 of a large rotule next the chitinous coat; whilst the distal rotule 

 varies in diameter from that of the connecting shaft to near equality 

 with the other. Margin of large rotule generally entire ; surface 

 flat and table-like or irregularly exflected ; smaller rotule obscurely 

 angular or occasionally notched. Shafts widening toward the larger 

 rotule, variable in length and thickness; always smooth, (ibid b. c. 

 d. etc.) 



Meas. Skeleton spicules 0"0066 by 0"0003 inches. Insequibiro- 

 tulates 0-00035 by O'OOOl inches. Diameter of large rotule 0.0007 

 inches; do, of smaller rotule 0*00015 inches. 



Hah. On stones and timbers in shallow water. 



Log. Lehigh River and tributaries ; also generally throughout 

 the Eastern United States. 



The first specimens of T. pennsylvanica were found in Novem- 

 ber 1881, among a miscellaneous collection of sponges from Lehigh 

 Gap,where they had grown, at an altitude of about 600 ft. above sea 

 level. They were minute, barely one fourth inch in diameter ; but were 

 welcomed with enthusiasm as the first representatives of the genus that 

 had been discovered in North America or, in fact, anywhere except in 

 the equatorial "giant of rivers." The year following, the species was 

 found growing at White Haven, on the Lehigh River, Pennsylvania, 

 (1000 ft. above the sea); in Lake Hopatcong, New Jersey, (alt. 1200 

 ft.); and was received from friends in several other parts of the coun- 

 try. My records show its receipt from at least eighteen different 



