16 Spong. 
SPONGIIDA. 
Under Tetractinellidce, Mcarshall, defined (14), Siliceous Sponges, with 
spicules of the pyramidal type, are grouped. They include : — 
Tethyopsis* Zittel, g. n., p. 9, pi. xi. fig. 3. Shape irregular ; main part 
of skeleton consists of very large parallel acerate spicules, radiating from 
the centre ; the surface of a layer of smaller three-forked anchors and 
still smaller tridentate forks, of linear and quadriradiate forms. Upper 
Chalk. 
PacTiastrella primceva described from the Upper Chalk ; Zittel, (14) p. 9, 
pi, xii. fig. 4. 
Calcauea. (14) p. 11, Zittel believes he has proved the existence of 
these in the fossil state ; three forms assigned by him to the group belong 
to a new division, Pharetrones, distinct from the Leuconea^ Sycones, and 
A scones of Haeckel ; they have chiefly uni-axial spicules, arranged parallel 
to each other in fibrous tracts ; form of sponge various ; canal system 
either that of Leucones or A scones, or consisting of a series of concentric 
cavities surrounding the cloaca ; surface formed either by main skeleton 
or by a special dermal skeleton agreeing with the epitheca of corals. 
Tables of distribution are given. They are solely fossil, and have not 
been found in the perfect state later than the chalk. To the group are 
assigned Eudea, Lamouroux, Colosponyia, Laubo, VerticillUes, Defr., 
Celyphia^ Pomol, Elasmocwlia^ Ilornor, Myrinecium, Goldfuss, Limnorea^ 
Lamouroux, Slellispongia, D’Orb., Ocuiispongia, From., Crispispongia, 
Quenstedt, Elasmostoma^ From., Diplostoma, From., Pharetrospongia, 
Sollas, and Liospongia, D’Orb. (the latter perhaps allied to Millepora, 
according to a note in JB. f. Mineral.). Most of these are recharac- 
terized by reference to their microscopic structure. 
Zittel (14) describes the following new genera of his Pharetrones : — 
Himatella, p. 29, Trias ; Peronella, p. 30, pi. xii, figs. 3 & 4, Trias to 
Upper Chalk; C'onocoeZ/a, Lower Chalk, and Eusiphonella, Upper Jura, 
p. 34 ; Corynella, p. 36, pi. xii. figs. 2, 5, & 6, Trias to Upper Chalk ; 
Sestrostomella, p. 40, Trias to Chalk ; Blastinia, Upper Jura, and Syno- 
pella, Chalk, p. 42 ; Pachytilodia, p. 46, “ Tourtia ” of Essen. 
Protosycon, g. n., id. 1. c. p. 48, pi. xii. fig. 7, White Jura {Sycones, 
Haeckel). 
* Name already applied to a recent Sponge, T. columnifer, by Stewart, 
Q. J. Micr. Sci. (n.s.) x. p. 181. — S. 0. K. 
