1863.] DR. J. S. BOWERBANK ON THE SPONGILLID^. 467 



I have dedicated this species to Mr. Lord as a slight acknowledg- 

 ment of the good services he has rendered to science by the collection 

 of this and numerous other valuable specimens of natural history 

 from unfrequented regions which he has explored. 



Spongilla Dawsoni, Bowerbank. 



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

 inconspicuous. Dermal and interstitial membranes abundantly spi- 

 culous ; spicula fusiformi-acerate, entirely spined ; spines numerous, 

 short, and conical. Skeleton-spicula acerate or sub fusiformi-acerate. 

 Ovaria spherical ; dermal spicula numerous, disposed in flat fasciculi, 

 or groups of spicula parallel to each other ; groups irregularly di- 

 spersed ; spicula acerate or subcylindrical, entirely spined ; spines 

 numerous, obtuse, and ill-defined. Sarcode aspiculous. 



Colour, in the dried state, emerald-green. 



Sab. River St. Lawrence, Montreal, Canada {Dr. Dawson, Mr. 

 Fowler, and Rev. A. Kemp) ; a lake near Brockville {Rev. A. Kemp). 



Examined in the dried state. 



About two years ago I received a small fragment of this species 

 from Dr. Dawson, who stated that it was found in the River St. 

 Lawrence, at Montreal ; but, as the fragment was destitute of gem- 

 mules and very small, there were not sufficient characters to warrant 

 a specific description of it. 1\\ October 1859 I received from the 

 same gentleman a further supply of fragments of this species, con- 

 taining ovaria, and giving a better idea of its form than those first 

 sent to me. The largest of the pieces sent was 1^ inch in length 

 and 21 lines in diameter, evidently a portion of a longer branch. 

 At the proximal end there is a short branch, 3 lines in length and 

 1 line in diameter ; and the distal end divides into two small branches 

 of similar dimensions to the first, thus satisfactorily indicating the 

 branching habit of the species. In several parts of this piece there 

 are ovaries imbedded in the Sponge, and there were many others in 

 the fragments of the same species that accompanied it. The general 

 external characters appear very like those of the European species 

 S. lacustris ; and, from this similarity, I have very little doubt of its 

 surface in the living state having been smooth and even, as in that 

 species. In the European species the branches spring from a broad 

 spreading base, about half an inch in thickness ; and I think it highly 

 probable that the American species will be found to possess the same 

 habit. I could not detect oscula on any of the fragments in my 

 possession. 



The dermal and interstitial membranes abound with tension-spi- 

 cula, and especially the dermal one, in which they seem to attain 

 their fullest degree of development. Their riormal form is fusiformi- 

 acerate ; but, from the abundant production of the spines at their 

 terminations, they frequently appear to be cylindrical rather than 

 acerate. They are dispersed on these tissues rather unevenly, abound- 

 ing in some spots, while they are comparatively scarce in others. 



The spicula of the skeleton are of about the same proportions as 



