STUDIES ON THE COMPARATIVE ANATOMY OF SPONGES. 1387 
relations of the subgastral sagittal triradiates to the fibres is, 
in many cases at any rate, identical with that of the corre- 
sponding spicules to the articulate tubar skeleton of a 
Syconoid. 
Thus, while in Leucandra the spicules of the primitive 
articulate skeleton become scattered and disjointed, in Lelapia 
they retain their mutual relationships, and indeed become 
much more intimately associated with one another to form 
spicular fibres,—this formation of fibres being greatly facilitated 
by their very peculiar shape. The fibres as a whole, however, 
become irregularly arranged, as do the individual spicules of 
Leucandra. 
Thus, then, I see no reason for altering the systematic posi- 
tion of the genus Lelapia as given in the genealogical tree at 
the end of my previous memoir (1). In other words, I regard 
Lelapia as an offshoot from the great family Grantide, 
coming off from the same branch which gave rise to the genus 
Leucandra. At the same time this way of thinking would 
not prevent us, if necessary, from accepting the Pharetrones 
as a distinct family and including Lelapia therein. 
B. Relationships to the Fossil Pharetrones. 
Professor Zittel, in his classical “ Studies on Fossil Sponges” 
(3), accepted Haeckel’s division of the Calcarea into Ascones, 
Leucones, and Sycones, but added thereto a new family, 
Pharetrones, which he regarded as of co-ordinate systematic 
value with Haeckel’s three groups. The following diagnosis 
was given of the new family :—“ Wand dick, mit ungeraden 
Astcanalen oder ohne alle Canale. Skeletelemente zu anasto- 
mosirenden Fasern angeordnet. Dermalschicht haufig yor- 
handen.” 
In this family Zittel placed, with one exception (Proto- 
sycon), all the then known fossil Calcarea, amounting to no 
less than fifty genera, and ranging from the Devonian to the 
Upper Chalk. 
These numerous fossil genera are naturally very imper- 
