REVISION OF FRESHWATER SPONGES OF SPONGILLIDAE 105 



Scattered but apparently widespread distribution in eastern parts 

 of the North American Continent, one species also recorded from 

 Ireland and eastern Europe, another ranging from central Europe 

 through the U.S.S.R. to China, Japan, and AustraUa, but absent in 

 America. 



Discussion. — The genus Heteromeyenia, as here restricted, now 

 includes only such species of the formerly conglomerate genus of that 

 name which possess free microscleres in the form of acanthoxea, while 

 those lacking microscleres altogether had to be transferred to An- 

 heteromeyenia Schroder, raised to full generic rank by de Laubenfels 

 (1936). That author, correctly avoiding Schroder's (1927b) redundant 

 subgeneric name Oxheteromeyenia for all species with acerate micro- 

 scleres, also redefined the available generic name Heteromeyenia Potts 

 and, in the absence of a designated genotype, proposed as its type 

 species H. repens Potts, now a synonym of H. baileyi (Bowerbank). 



In spite of Schroder's (1927b) convincing demonstration of the close 

 interrelationship of aU species formerly grouped in Potts' unrestricted 

 genus Heteromeyenia, his interspecific comparative studies of the 

 gemmular porus tube have only added to the already existing taxo- 

 nomic confusion. Having established for the first time the heterogeneous 

 character of the gemmoscleres in the type of Spongilla baileyi, he had 

 no hesitation in considering, in addition to the clearly synonymous 

 H. repens, even some species of the former genus Carterius as mere 

 races of Bowerbank's nominal species, an arrangement which cannot 

 possibly be retained. While in the H. baileyi complex the gemmo- 

 scleres are heterogeneous both in regard to length and shape of rotules, 

 the birotulates of the Carterius stepanowii complex differ only in 

 length, and possess almost to fully identical rotules. Although, as 

 shown by Schroder (1927b), the separate status of the genus Carterius 

 is fully unjustified, aU its previous species moreover share an ad- 

 ditional criterion, i.e., the foraminal cirrous appendages or their 

 visible rudiments, which in the H. baileyi complex are lacking alto- 

 gether. The revised genus Heteromeyenia Potts therefore must be 

 considered to consist of two morphologically distinct groups, both 

 having acerate microscleres in their symplasm and dermal membrane. 

 The first, 'with two distinct classes of heterogeneous gemmoscleres 

 and without foraminal projections, is represented by the H. baileyi 

 complex, by the insuflSciently known H. longistylis Mills, and perhaps 

 also by the stiU dubious H. insignis Weltner; the latter two could 

 not be examined during the present study. The second, displaying 

 more or less only two length groups in their gemmoscleres and con- 

 spicuous foraminal tendrils on their gemmides, comprises H. stepanowii 

 (Dybowsky) with its "varieties" arndti, bohemica, palatina, and 

 petri, H. latitenta (Potts), H. tentasperma (Potts), and H. tubisperma 



