1887.] NATURAL SCIENCES OF PHILADELPHIA. 239 



recognizing their novelty. Its habit was to creep over submerged 

 timbers and sticks, the leaves of water j^lants, the slender stems 

 of Nitella etc., generally, when upon a smooth surface, assuming 

 vermiform lines, one fourth inch or more in width, along Avhich the 

 gemmules were left in scattered groups. Five years later I found 

 it growing in a similar fashion in Lake Hopatcong, New Jersey. 



I have been thus particular to give the history of this species be- 

 cause of the doubt that may disturb other minds than my own, 

 whether it may not be identical with Mexjenia {Spongilld) baileyi, of 

 Bowerbank ; the sponge that Prof. Bailey gathered "from a stream 

 on the Canterbury Road, near West Point, New York." Admit- 

 ting the resemblance of the spicules that Dr. B. has represented and 

 described, to some of those pertaining to tLij species, I. would call 

 attention to the fact that he has neither described nor represented 

 the more numerous class of birotulate spicules, which, under the 

 supposition that the species were identical, would be a singular 

 omission. If stress be laid upon the resemblance of the dermal 

 spicules of the two forms, I remark that two species of Carterius 

 ( C. tubisperma and C. latitenta) have a similar one. The type spec- 

 imen from which the description by Dr. B. was prepared, was a 

 very small one and I have not had access to it for final comparison. 

 For these reasons and while a doubt remains as to their identity^ 

 I incline to hold fast by my descriptive title. 



(2) Heteromeyenia argyrosperma, Potts. Proc. Acad. Nat. Sci. Phila. 1881, p. 

 160. (PI. VI. fig. i.) 



Spongilla argyrosperma, Potts. (Proc. Acad, etc., 1880, p. 357.) 



Sponge minute, encrusting ; color gray ; texture loose. 



Gemmulpe abundant; relatively large, on account of the unusually 

 thick granular crust, through wliich the distal ends of the longer 

 class of surrounding bii'otulates sometimes project, or support portions 

 of it in many conical prominences. (PL VI, fig. i.) Foraminal 

 tubule somewhat prolonged; smallest at the extremity. Color silvery 

 white, suggesting the specific name.^ 



Skeleton spicules rather slender, cylindrical or sub-fusiform ; 

 abruptly pointed, sparsely spiniferous ; spines small, pointed ; pro- 

 jecting forward towards the extremities of the spicules. (PI. XI, 

 fig. i, a.a.) 



ilf this and some other of the specific names, derived from the Greek, are 

 found not to be in "good form," I can only regret that the discovery of the rule 

 came too late, and that many alterations of name may be a worse error. 



