118 U.S. NATIONAL MUSEUM BULLETIN 2 72 



of equal size, with a large number of small crenulate teeth on their 

 slightly recurved margin; length range of longer class 50-75 ^i, width 

 range 6-8 n; length range of smaller class 30-40 /x, width range of shaft 

 3-4 M, of rotule 25-27 m- 



Gemmules abundant in mature sponge, ranging in diameter 320- 

 350 n; pneumatic layer weU developed and granular, consisting of 

 minute spherical au- spaces; gemmoscleres embedded in this layer 

 strictly radially, their longer class protruding from the outer gemmular 

 membrane; foramen more or less simple without a discernible porus 

 tube, but present on a conical elevation. 



Distribution. — Apparently restricted to the eastern half of the 

 North American Continent, ranging from Louisiana to Canada. 



Color in life. — Recorded as light green. 



Discussion. — The great variability of spicular components of the 

 gemmular armature, a weU-known phenomenon in most spongUlids 

 with heterospecific gemmoscleres, is perhaps more pronounced in 

 A. ryderi than in other species of this complex. The gemmoscleres of 

 A. ryderi are hardly identical in any two specimens of the same locality 

 and tend to be greatly different in distant populations. Malformations 

 of gemmoscleres are quite frequent (see pi. 10, fig. 2) and the longer 

 as well as the shorter class are thus affected. The "varieties" baleni 

 and walshii of this species certainly fall into the usual morphometric 

 range of the nominal species, and the retention of these two slightly 

 aberrant sponges as distinct races seems unjustified. The species 

 H. macouni MacKay (1900), not present in the material available for 

 this study, was relegated by Gee (1931e) to a synonym of H. baleni, 

 so that it too must now be considered to fall clearly within the mor- 

 phometric range of A. ryderi, as here revised. 



As mentioned in the generic discussion, H. conigera Old (1931) 

 most probably is nothing more than a malformed specimen of A. 

 ryderi. An examination of the holotype of the former clearly demon- 

 strated that the megascleres are fully comparable with those of any 

 range of the latter species, and that the longer gemmoscleres are 

 almost inseparable from those of A. ryderi in shape as well as in 

 measurements (see pi. 10, figs. 13-15). Omitting the characteristic 

 cone like swellings under the rotules of the smaller class of gem- 

 moscleres, even the general shape of their rotules is similar in both 

 species. Considering the frequence of malformed birotulate gemmos- 

 cleres in nearly all genera displaying them, it appears very likely that 

 these particular "swellings" in H. conigera are the result of a freak 

 deposit of silica due to some adverse environmental factors. This 

 assumption appears strengthened by the great variability displayed 

 by the shorter class of gemmoscleres in H. conigera, and that this 

 species apparently has been found only once. 



