190 PROCEEDINGS OF THE ACADEMY OF [1887. 



possible diminution of the water way and contamination of the drink- 

 ing water by its further growth. 



I have not had an opportunity to examine the type specimen from 

 Avhich the above description by Dr. Bowerbank was prepared, but 

 from the study of fragments received from Mr. Desmond Fitz- 

 Gerald, Chief Engineer of the Boston Water Department, collected 

 by him from Farm Pond and Cochituate Reservoir, near the head of 

 the water system of that city (in all pi'obability the same that Dr. 

 Bowerbank describes), I am induced to class this as one of the many 

 varieties of S. lacustris. In the dry state the sponge is very friable 

 and its dermal surface soon crumbles off, which may in a measure ac- 

 count for the apparent absence of dermal and interstitial spicules 

 from Dr. B's specimens. Mr. H. J. Carter records the finding of 

 acerate, dermal spicules in those received by him from the same local- 

 ity, and I have found them, though few in number, in the fragments 

 .sent to me. We may regard, therefore, the dermal and interstitial 

 surfaces of S. paupercula as not aspiculous and assert that those 

 found are not entirely smooth ; as in nearly all a few spines may be 

 discovered, ])articularly near the extremities. 



The gemmule spicules are equally scarce and without pronounced 

 character ; their relative smoothness and greater proportionate length 

 than in most other forms of this species are the noteworthy points. 

 The gemmules are quite numerous, large and entirely devoid of 

 "crust." Their shrunken contents, appearing through the transparent, 

 crustless chitin, give them a peculiar waxen cast. It will be noted, 

 us has before been incidentally njentioned, that in this, as in other 

 cases, a paucity of gemmule spicules attends, as a necessary conse- 

 quence, the absence of an enveloping crust. 



S. lacustris, \ :ir. dawsoni, Bowerbank. VnK. Zool. Soc. London 1S63 pg. 4G7. 



"Sponge sessile, branching ; surface smooth. Oscula and pores 

 inconspicuous. Dermal and interstitial membranes abundantly 

 spiculous; s2)icula fusiform-acerate, entirely spined ; spines numer- 

 ous, short and conical. Skeleton spicula acerate or sub-fusiform- 

 acerate. Ovaria spherical ; dern)al spicula numerous, disposed in 

 iiat fasciculi or groups of s})icules parallel to each other (?) ; grouj)s 

 irregularly dis])ersed ; spicula acerate or sub-cylindrical, entirely 

 spined; spines numerous, obtuse and ill defined. Sarcode aspiculous. 

 Color in the dried state emerald green." Bowerbank. 



>S. _/?ea;t.spma, Dawson. Syn. Canadian I^at. and Geol. Sept. 1875. 



/V. lacusfrioides, l*otts, Syn. 



