246 MisceUaneous. 



more variable in size, are occasionally spined, and liave their rays 

 more prolonged and more delicately terminated. 



It is in the singular character of the spicules surrounding the 

 gemmula3 that this sponge must attract peculiar attention. By the 

 system of H. J. Carter, Esq., the freshwater sponges are now classi- 

 fied into six genera, besides some conditional designations of forms 

 in which the typical features are as yet undiscovered. These six, 

 Sj>on(/illa, Meyenia, Beteromei/enia, Tahelh, Parmula, and Carteriiis, 

 may again be associated into two groups, one of them including only 

 the genus SpongiJla, characterized by the linear acerate spicules sur- 

 rounding the gemmulae ; and the other comprising all the other 

 genera, where the spicule of corresponding significance is a birotulate, 

 or some easily recognized derivative of that type. Within this latter 

 and larger group intermediate forms, connecting the defined genera, 

 are frequent, and the location of species upon one side or other of 

 the distinctive line comparatively unimportant. Heretofore, be- 

 tween the genus Spongilla and those genera composing the other 

 group there has been " a great gulf fixed." One case only in the 

 past has suggested their possible association, or the development of 

 one group from the other. 



In Meijenia acuminata. Potts (Proc. Acad. Nat. Sci. Philad. 

 1882, p. 69), since regarded as a variety of M. fiaviatiUs, the shafts 

 of the birotulates are prolonged at each extremity, forming acumi- 

 nate terminations some distance beyond the surface of the rotules. 

 In position also these spicules are abnormal, lying flat upon the 

 chitinous coat, instead of resting upon one rotule, their shafts taking 

 the position of radii, as is usual in this form. In fact, we have the 

 spicules of a Meyenia occupying the ordinary positions, and in 

 degree approximating the forms of those peculiar to the Spongilloe. 



In the present instance their intermediate character is still more 

 striking, and while theii' form and position probably more closely 

 associate them with the genus Spongilla, in which the species has 

 now been placed, the grouping of the ray-like spicules clearly suggests 

 Meyenia. It has been an altogether unprecedented experience with 

 the author to hesitate between these two genera, and it will be no 

 cause of surprise if the future teacher shall shift it from its present 

 position. 



It must not escape notice that in both of these instances the gcm- 

 mula3 are without " crust ;" that it is difficult to understand how 

 birotulates could be supported in their ordinary positions xvithont 

 these imbedding granules; and that we may not uni'casonaljly infer 

 that the change in position has induced tlie modification of type that 

 we here find. 



This collection of sponges, including the new species, has been 

 examined coincidcntly by H. J. Carter, Es(]., F.R.S., and their 

 identification and this dopcription are believed to meet his approval. 

 Proc. Acad. Nat. Sci. riiilad, April (>, 1886, p. 227. 



