1887.] NATURAL SCIENCES OF PHILADELPHIA. 221 



M. fiuviatilis certainly cannot be called a branching sponge, but 

 in some localities, particularly when growing on the lower side of 

 timbers etc. or in a rapid current, I have found it bearing incon- 

 sequent processes about au inch in length. In color it inclines to a 

 light brown or yellowish, but in our clear northern lakes, where it 

 grows in large patches exposed upon the upper surface of stones, it 

 is described as of a vivid green. 



Meyenia fiuviatilis, var. meyeui. 



Spongilla meyeni, Carter. 



Skeleton spicules sparsely microspined, long, cylindrical. Gem- 

 mules spherical ; chitinous coat and granular crust relatively thick, 

 Birotulates often in two or three partial series ; shafts long, cylin- 

 drical, generally smooth ; rays of the rotules long, conical, deeply 

 divided. An occasional spicule may be found of an intermediate 

 character between the acerates and the birotulates; that is, it 

 resembles a short acerate with Avhorls of short spines about one 

 fourth its length from either end. 



In his Monograph of 1881 INIr. Carter dropped this one of his 

 original species of Bombay sponges from his classification, merging 

 it Avith M. fiuviatilis. For several reasons I incline to retain it as a 

 variety of that species. The size of the birotulates is far greater 

 than the average in the typical sj^ecies, and their cylindrical shafts 

 and symmetrical forms give them a peculiar beauty. Their occa- 

 sional arrangement in multiple series is not unique, but the habit 

 was first noticed in this variety. 



Ifeas. Skeleton spicules 0-0108 by O'OOOl inches. Length of 

 average birotulate O'OOIS inches. Diameter of rotule O'OOl inches. 



M. fiuviatilis, form astrosperma, Potts. Syn. Proc. Acad. etc. 

 1880, p. 357. 



The name "star seeded" was applied before the author had the 

 opportunity to compare this with the Eui'opean tyj^e, or even 

 with collections from other parts of this country. It is a beautiful 

 form of the species, Avith birotulates sufficiently scattered over the 

 surface of the gemmule, to show as stars upon a silver dome (PI. V. 

 fig. V.) It Avas found at Lehigh Gap, Pennsylvania; but cannot 

 claim to be even a variety. 



3f. polpnorjjha, Syn. was suggested to me by the great numbers 

 of misshapen or incomplete forms surrounding the statoblasts ; as in 

 (PI. IX, fig. iv, e, e, e.) These, as my friend Mr. Carter has shoAA^n 

 me, are nearly all abortive birotulates ; and Avhen aa'c inquire into 

 their cause we find that they occur almost solely upon gemmules 



