TREMADICTYON. 195 
DESCRIPTION OF GENERA AND SPECIES. 
JURASSIC SPONGES. 
Sub-order,—HEXactINELLIDa. 
Growp.—DIcryvonina. 
Genus.—Tremapioctyon, Zittel. 
1877. Studien uber fossile Spongien, I. Abhandl. der k. bayer. Akademie der Wiss., Cl. ii, 
Bd. xiii, Abth. i, p. 46. 
Syn.—Scyphia, Auct. (in part); Cribrospongia, d’Orbigny (in part); Cribro- 
scyphia, Fromentel (an part); Cribroccelia, Htallon (in part); Retispongia, 
Quenstedt (in part). 
Sponges cup-, platter-shaped, or cylindrical, with wide central cavity. On 
both the outer and inner surfaces of the wall there are tolerably large oval or 
rhomboidal ostia, disposed in rows alternately. Radial canals blind. The lattice- 
like skeleton of the wall and basal portion of the sponge consist of large irregular 
meshes, resulting from the frequent thickening and expansion of the spicular rays. 
The spicular nodes are compact. When well-preserved both surfaces of the wall 
are covered by an extremely delicate lattice-like membrane of amalgamated six- 
rayed spicules, which hkewise extends over the ostia. The basal, or root, portion 
of the sponge is nodose and without ostia or canals. Type species Tremadictyon 
(Scyphia) reticulata, Goldfuss, sp. (‘ Petref. Germ.’ vol.i, p. 11, pl. iv, figs. 1 a—d). 
The above description is taken from that given by Von Zittel, based on 
specimens from the Upper Jura of Wirtemberg, in which the skeletal structures 
have been preserved. The earliest recorded appearance of the genus is by 
Dunikowski, in the Lower Lias of Schafberg, near Salzburg (‘ Denkschriften der 
k, Akad. Wissensch. Wien,’ vol. xlv, 1882, p. 179, pl. iv, figs. 42, 43); it occurs 
abundantly in the Swiss Jura, as well as in the Upper Jura of Wiirtemberg. 
1. Tremapictyon sparsum, Hinde, sp. nov. Plate X, figs. 1, la. 
Only fragments of this species are known, they indicate that the sponges were 
open cup-shaped, having walls from 4 to 12 mm. in thickness; the surface ostia 
are oval, ranging from 1‘5 mm. to 3 mm. in length, and the mesh-walls between 
