NORTH AMERICAN PORIFER^. PART II. 519 



between the tubes, and the fistular aspect is consequently almost lost, PL xvi, fig. 5. . This 

 leads into the following form which may be styled normal or typical. 



Loc, Nassau, in Soc. Coll. 



Variety alha. The name alludes to the whiteness of the fibres. The preceding form 

 merely increases in size with its widely separated fistular tubes (PL xv, fig 4), and with a 

 dense skeleton between, rounding upon the top until quite a tall, stovit head is built up, 

 which in its most perfect form is quite symmetrical, but this leads into fistulose forms, such 

 as the figure (PL xvr, fig. 7). The primary tufts are very large in this variety, as in variety 

 isolata. With this I should also associate the large, flat-topped, large apertured and loose 

 textured specimens, which have small bases of attachment and rounded swelling sides. 

 There are also some very interesting forms which lead from these into the next. They 

 have the same surface and texture, but instead of many, have only one large aperture in 

 the centre of the elongated circular head. 



Loc, Biscayne Bay, Nassau, in Soc. Coll. 



Variety solitaria. This (PL xvi-, fig. 3) has only one large aperture, with a very much 

 elongated, and altogether fistulose, aspect. The difiference consists in the absence 

 of the fibrous tufts over considerable spaces, giving the surface thus changed a peculiarly 

 solid aspect. This leads into sub-species meandriniformis. 



Variety hirsuta} This (PL xvi, fig. 4) is distinguished by the enormous length of the 

 tufts, and the great number of the orifices and channels, rendering this variety exceed- 

 ingly soft, and the surface particularly cavernous in appearance. 



Loc, Nassau, in Soc. CoU. 



Sub-species meandriniformis. 



Sjmngia meandriniformis Duch. et Mich., Op. cit., p. 33. 



This, the well known Velvet sponge of commerce (PL xvi, fig. 2), is undoubtedly the 

 form described by Duchaissing and Michelotti. It difiers from the preceding in its extreme 

 forms by the absence of the pointed bundles or tufts, and the fibres also are perhaps slightly 

 finer. The absence of the pointed tufts gives a smoother surface, since, as in the preced- 

 ing variety, these are mainly composed of coarse primary fibres loaded with foreign matter, 

 whereas the connecting or secondary fibres are composed of pure keratose. The surface is 

 also remarkable for the protruding flattened cushions of fibre which slightly resemble the 

 convoluted ridges of a meandrina. Sometimes these cushions are transformed into long, 

 solid brushes, or pencils of fibre. 



Loc, Biscayne Bay, Nassau and Key West, in Soc. Coll. ; Island of Fernando Noronha, 

 Havana, Mauritius, in CoU. Mus. Comp. Zoology. 



Variety barbara. 



Sjiongia cavernosa Duch. et Mich., Op. cit., p. 30. 

 " barbara " " " " p. 31. 



The irresolvable uncertainty which surrounds the identity of the actual form described 

 under this name by Lamarck, has led me to think that its utter abandonment would be 

 the best course to pursue. That any two independent workers should describe precisely 

 the same form by this name seems to me improbable, in consideration of the fact that 



^Spongia uliHs Duch. ct Mich. I have not been able to same as the variety " liirsula" or '^porosa" of Spongia 

 i dentify tliis species or variety, but I tliiiik it may be the gossypina. 



