SILICIOUS AND HORNY SPONGES WILSON. 429 



Genus MYXILLA O. Schmidt sensu Lundbeck (1905). 



Myxilla O. Schmidt, 1862, p. 71. Not Myxilla Topsent, 1892, p. 108, lS04c, 

 p. 11, 1004, p. 16S. — Emended LttnDbeck, 1005, p. 131. — Kirkpatriok, 

 1008, p. 27.— Topsent, 1013, pp. 623, 625.— Hentschel, 1914, p. 07. 



Myxilla part, Ridley and Derby, 18S7, p. 128.— Dendy, 1895, p. 29; 1905, 

 p. 168. 



Dendoryx Gray plus Lissodcndori/x Topsent part, Topsent, 1802, p. 97; 

 1894c, p. 9 ; 1904, pp. 172, 173. 



Habitus varying; incrusting, massive, lamellate, club-shaped forms 

 all occur. Main skeleton a polvspieular reticulation of monactinal 

 megascleres, sometimes very diffuse; fibers differentiated in some 

 species. Skeletal spicules generally spinose styles, sometimes smooth. 

 Special ectosomal megascleres present; these ordinarily diactinal and 

 most often smooth but sometimes spinose. Microscleres isancoras, 

 most often tridentate, to which sigmas may be added. 



The generic synonomy is involved. Myxilla, as used by Ridley and 

 Dendy, 1887, and Dendy, 1895, 1905, is placed in the Ectyoninae but 

 is conceived as intermediate between the Mycalinae and Ectyoninae, 

 including species both with and without echinating spicules. Dendy 

 would regard the former as the primitive forms, the latter as de- 

 rived forms in which the spined styles (tylostyles) have been re- 

 tained although they have lost their original echinating arrangement 

 and " have passed into the main skeleton " forming a reticulation 

 with one another. A necessary corollary is to draw the further de- 

 duction that in some species the megascleres have lost their spines. 



From this very comprehensive genus Topsent, 1892, 1894e\ 1904, 

 subtracts the species without echinating spicules (mycaline), leaving 

 Myxilla as a distinctly ectyonine genus. For the mycaline species 

 with spined megascleres he restores Dendoryx Gray and for those 

 with smooth megascleres establishes Lissodendoryx. 



It was pointed out by Dendy, 1895 (p. 29), and by Thiele, 1903 

 (p. 953), that Dendoryx as used by Topsent is not defensible from 

 the nomenclatural standpoint, since the type species of Myxilla, M. 

 rosacea (Lieberkiihn),has no special echinating spicules and is & Den- 

 doryx in the sense of Topsent. If, therefore, Topsent's subdivision 

 of Myxilla is carried out, the name Myxilla must be used instead of 

 Dendoryx, and some other generic name or names be found for the 

 ectyonine species of Myxilla in the sense of Ridley and Dendy, and 

 Dendy. Lundbeck 1905, followed by others (Kirkpatrick, Hent- 

 schel, Topsent), introduces the nomenclatural change of Myxilla for 

 Dendoryx. 



As to the ectyonine species of Myxilla in the sense of Ridley and 

 Dendy, Topsent, 1913 (p. 623), refers some to Stylostichon Topsent, 

 others in which the skeleton is reticulate to Dendoryx Gray emended, 



