1887.] NATURAL SCIENCES OF PHILADELPHIA. 211 



(b) Margins of hirotulate spicules rayed. 



5. Skeleton spicules either smooth or microspined ; dermals want- 

 ing; birotulates short, shafts generally smooth; margins of rotules 

 irregularly rayed. (PI. V tig. v ; PI. IX figs, i, to iv.) 



M. fluviatilis. 



6. Birotulates in two or three series. M. (Ej)hydatia) mulleri. 

 (See also genus Pleiomeyenia.) 



7. Parasitic on *S'. lacustris; foramina funnel shaped. 



M. bohemica. 

 Si. Birotulate spicules generally malformed; shafts with enormous 



spines, etc. (PI. IX fig. v.) M. robusta. 



II. Birotulates rather long, shafts smooth; margins of rotules la- 



cinulate. (PI. X fig. ii.) M. millsii. 



10. Rays and spines of birotulates subdivided or microspined. (PI. 

 IX fig. vi.) M. subdivisa. 



11. Dermal spicules with long, erect spines; birotulates long, 

 spined; rays incurved. M. baileyi. 



12. Birotulates rather long; margins crenulate or granular. 



M. capewelli. 



IH. Gemmules flask-shaped; a})ertures terminal; birotulates very 



short, obscure. M. anonyma. 



14. Shafts of birotulates much spined. M. ramsayl. 



15. Birotulates many times longer than the diameter of the hooked 

 rotules; shafts spiniferous. (PI. V, fig. vi. PL X, fig. v.) 



M. crater if ormis. 

 1(>. Gemniule birotulates long, club-like. Dermal spicules also 

 birotulate, minute. (PI. X, fig. iii and iv). 



31. everetti. 



17. Gemmule birotulates long, spinous; margins of rotules notched: 



dermal spicules stellate. (PI. X, fig. vi.) M. plumosa. 



(ci) Margins of birotxdate spicules entire. 



(1) Meyenia (Trochospongilla) erenaceus, Ehrcnburg. Sec Vejclovskj^'s "Di;ig- 

 nosis." |>. 177 



In his description Prof Vejdovsky has not, I think, invested the 

 parenchyma surrounding the gemmulte of this sj^ecies with sufficient 

 importance. From specimens which he has kindly sent to me, I am 

 led to regard this feature, at least to this degree, as unique amongst 

 the sponges, and I regret my inability to furnish an illustration of 

 it. I do not know whether the sponge mass bears any external 

 resemblance to that of M. leidyi, but they are unquestionably distinct 

 species. 



