SILICIOUS AND HORNY SPONGES WILSON. 423 



and Desmacella are used sensu Topsent, in that the former is con- 

 ceived as having a skeletal framework which, if fibrous, is only in- 

 conspicuously so; while in Desmacella the framework includes well 

 developed fibers. 



Thiele, 1903, points out that the name Desmacella should be can- 

 celed and replaced by Biemna Gray, and for Biemma sensu Top- 

 sent and authors he proposes Tylodesma. Wilson, 1904, accepts 

 these nomenclatural changes. 



Dendy, 1905 (p. 155), retains the subfamily, placing it in the 

 Haploscleridae, and does not follow Thiele in nomenclature; Des- 

 macella is defined as having a reticulate skeletal framework. 

 Henschel, 1911, follows Topsent, 1894c, in transferring the genera to 

 the Desmacidonidae (Mycalinae) ; Desmacella is defined as having 

 a reticular skeleton, Biemma as having a halichondrioid skeleton. 

 Hentschel, 1912 (pp. 350-354), adopts Thiele's nomenclatural 

 changes, using Biemna Gray in place of Desmacella authors and 

 Tylodesma Thiele for Biemma authors. He continues to define the 

 skeleton of Tylodesma as halichondrioid, but this distinction from 

 Biemna is certainly vague, as is shown by the fact that he is forced 

 to assign to the latter genus not only species with definitely defined 

 fibers but others with only loose tracts of spicules. Topsent, 1913 

 (pp. 50, 51), accepts Thiele's nomenclatural changes, as do Hallman, 

 1916, and Stephens, 1921. 



Since Thiele's nomenclatural changes have been so generally 

 adopted the name of the subfamily should be changed to Biemninae. 



Dendy, 1921& (p. 56), brings the case up again. He accepts 

 Thiele's nomenclatural change in so far as it affects sponges like 

 Desmacidon peachii Bowerbank, which are thereby renamed Biemna 

 Gray (a brief review of the data is given in Wilson, 1904, p. 135), 

 but is unwilling to accept Tylodesma. " If there is one thing clear 

 in the whole muddle" he thinks "it surely is that Tylodesma is a 

 pure synonym of Desmacella.' 1 '' I can not agree with Dendy that 

 Desmacella should be retained, for the following reasons : 



Desmacella Schmidt, 1870 (p. 53, also pp. 3, 77), was set up to 

 cover certain new species, two Hamacanthas (johnsoni and species) 

 and Desmacidon peachii Bowerbank. It is therefore in part synony- 

 mous with Hamacantha Gray, as Vosmaer (1887) pointed out. 

 Schmidt, 1880 (p. 82), withdrew the Hamacanthas, but the genus re- 

 mained in part at least synonymous with Biemna Gray, of which 

 Desmacidon peachii may fairly be taken, as is now generally done, 

 as the type species. This only leaves Schmidt's new species, pumilio 

 and vagabunda (Schmidt 1870), as a body for his genus. 



