1887.] NATURAL SCIENCES OF PHILADELPHIA. 219 



without a suggestive guidance ; being about one sixteenth inch in 

 diameter. The first was found, accidentally, on a mount containing 

 another sponge and a very careful and almost despairing search 

 was required before another was discovered. Its generic classification 

 has been somewhat doubtful. But for its entirely abnormal gemmules 

 and the geographical dislocation of the sjjonges, it might readily 

 have been associated with the highest serial form of Tubella joenn- 

 sylvanica ; viz., that in which the rotules are most nearly equal. 

 For tlie reasons mentioned it seems best to separate them and 

 place it in the genus Meyenia, where it differs noticeably from M. 

 gregaria, (found upon the same stem) and from 31. leidyi ; each of 

 which species has a capsular envelope ; also from 31. erenaceoUs with 

 its unique parenchyma of oblong cells. I have therefore made it a 

 new conditional sjjecies. 



(b) 3fargins of birohdates rayed. 

 (5) Meyenia fluviatilis, (S. fluviatilis) Auct. (PI. Y, fig. v, PI. IX, figs, i to iv.) 



Syn. European, See Vejdovsky "Diagnosis." p. 178. 

 " Asiatic, 1849, Spongilla meyeni, Carter. 

 " American : — 

 1875 3Ieyenia (Spongilla) asjyerima, Dawson. 



stagnalis, 

 1880 " " astrosperma, Potts. 



" " " 2^olynior2)ha, " 



1882 " var. acuminata, " 



1885 " " mexicana, " 



" " " angustibirotidata, Carter. 



" gracilis, 

 ''Massive, lobate. Structure friable, crumbling. Color light yel- 

 low-brown. Skeleton-spicule curved, fusiform, gradually sharjj-. 

 pointed, smooth ; often spiued and often centrally inflated. Stato- 

 blast globular ; aperture infundibular ; crust thick, composed of 

 granular or microcell substance, charged with birotulates whose 

 umbonate disks are deeply and irregularly denticulated, arranged 

 parallel to each other and perpendicular to the chitinous coat." 

 Carter. (Ann. and Mag. 1881 p. 92.) 



My observations upon this species as found abundantly in all 

 parts of North America, and in very variable forms, may be sum- 

 med u}) as follows. — 



Sponge sessile, massive, rarely throwing out short branches an 

 inch or less in length. Color varying from light yellow or brown 

 to a light green, according to exposure. Surface tuberculated or 



