276 PROCEEDINGS OF THE ACADEMY OF [1887. 



Fig. III. Spongilla fragilis. From Calumet River, Illinois :-a,a, 

 skeleton spicules ; h, c, d, e, variable parenchymal spicules; 

 ///, spined, spherical forms frequently seen throughout 

 the species. Collected by B. W. Thomas. 



Fig. IV. Spongilla jragilis, var. minuta. From Lehigh Gap, Penn- 

 sylvania :-a,a,a, skeleton spicules ; b,b,b, long, spined, 

 acuminate, "parenchymal spicules ;" c,c,c, spherical and 

 amorphous forms. 



Fig. V. Spongilla igloviformis. From Donghty's Pond, Absecum, 

 New Jersey -.-a, a, c, skeleton spicules ; b,b, "parenchy- 

 mal spicules" nearly equally long, but more spinous. 



Fig, VI. Spongilla aspinosa. From Doughty 's Pond, Absecum, 

 New Jersey -.-a, ordinary skeleton spicule ; b, skeleton 

 spicule ; actiate or rounded at one end; c, d, malformations 

 of skeleton spicules ; e,e,e, smooth dermal spicules ; ///, 

 globular or discoidal masses of silica, frequently observed 

 in this species. 



Plate IX. 



Fig. I. Meyenia fiuviatilis. From an English type, received from 

 H. J. Carter :-a and 6, spined skeleton spicules ; c, smooth 

 do.; d,d,d, birotulate gemmule spicules sometimes with 

 acuminate umbos ; e,e,e, end view of rotules. 



Fig. II. Meyenia fiuviatilis var. acuminata. From Boston, Massa- 

 chusetts -.-a, ordinary skeleton spicule ; b,b, slender forms 

 ofdo. ; (;,c,d,d, acuminate or misshapen birotulate gem- 

 mule spicules. 



Fig. III. Meyenia fiuviatilis, form astrosper7na, syn. From Lehigh 

 Gap, Pennsylvania :-a,a, skeleton spicules ; b,b, birot- 

 ulate gemmule spicules ; d,d, malformed do. ; c, group of 

 rotuhr ; e,e, single rotules showing an ordinary distrib- 

 ution of the rays. 



Fig. IV. Meyenia fiuviatilis. From Chester Ch-eek, near Lenni, Penn- 

 sylvania. -a, proper skeleton spicule; 6, malformed do.; 

 d,d,d, short, robust birotulates ; c,c,c rotules with symmet- 

 rical, conical rays, sub-spined at margins ; e,e,e,e, malform- 

 ations of birotulates. frequent in this specimen. 



Fig. V. Meyenia robusta. From Honey Lake Valley, California;- 

 a, a, smooth skeleton spicules ; b,b,b, coarsely spined gem- 



