REVISION OF FRESHWATER SPONGES OF SPONGILLIDAE 115 



radially, the outer rotules of the smaller series not quite extending to 

 the outer genunular membrane, those of the longer series often con- 

 siderably surpassing it; foramen shghtly elevated or distinctly tubular; 

 if porus tube present, its distolateral margins always without cirri. 



Sponges forming flat to massive encrustations, with surfaces ranging 

 from smooth to irregularly lobose; association with zoochlorellae 

 frequent, and consequently coloration often a light green. Con- 

 sistency ranging from soft to moderately firm. 



Scattered but apparently widespread distribution in eastern parts 

 of the North American Continent, some species also recorded from 

 Ireland. 



Discussion. — The subgenus Anheteromeyenia, erected by Schroder 

 (1927b) for the inclusion of those species of Heteromeyenia which lack 

 free microscleres, was elevated by de Laubenfels (1936) to full generic 

 rank. The failure of both these authors to designate a generic type 

 species has led to the consideration of S. argyrosperma Potts as the type 

 species of Heteromeyenia sensu lato by Jewell (1952). However, 

 Jewell did not actually designate the type species mentioned but 

 merely stated in deahng with the genus Heteromeyenia: "No type 

 species was designated, but as H. argyrosperma was first to be men- 

 tioned and first described it has usually been regarded as the genotype" 

 (p. 451). Since S. argyrosperma Potts lacks free microscleres, and 

 therefore cannot possibly be considered as the type species of 

 Heteromeyenia as here restricted, it is here^\^th designated as the type 

 species of Anheteromeyenia, while H. repens Potts (now a synonym 

 of H. hayleyi (Bowerbank)) must be considered to represent the type 

 species of Heteromeyenia sensu stricto. 



The very few species comprising the genus Anheteromeyenia can be 

 separated into two morphologically distinct groups. In one, represented 

 by A. argyrosperma, the gemmules possess a distinct porus tube and 

 their two length series of gemmoscleres are quite similar in shape. 

 The other is represented by the extremely variable A. ryderi vath some 

 of its "varieties," by A. pictovensis, and by the still somewhat dubious 

 and probably malformed species A. conigera and A. biceps. In this 

 group the gemmoscleres are distinctly heterogeneous in length as well 

 as in shape, and the micro pyle of the gemmules is devoid of a distinct 

 porus tube and only shghtly elevated. While the present studies 

 revealed no significant morphometric differences between the nominal 

 species of ^. ryderi and those of its former "varieties" A. r. haleni and 

 A. r. walshii, the different structure of the spicular components of 

 A. pictovensis makes it plausible to consider this spongilhd a distinct 

 species. The apparently characteristic gemmoscleres of A. conigera 

 agree morphometricaUy with those usually found in A. ryderi, ex- 

 cepting those conical "sweUings" around the rotules of the shorter 



279-430— 6S 10 



