DIPLODICTYON. — SCLEEOKALIA. 145 



Genus DIPLODICTYON, Zittel, 1877. 



DiPLODICTYON HETEKOMORPHUM, HeUSS, Sp. 



1845. Scyphia heteromorpha, Reuss, Bohm. Kreide, p. 74, t. 18. f. 1, 2. 

 1877. Diplodictyon heteromorphum, Zitt. Studien, I Ab. p. 59. 



Microscopic fragments of the spicular mesh. 



Distribution. Planer-Kalk: Schilling, Bohemia {coll. Zitt.). 



Diplodictyon Baypieldi, Hinde, n. sp. (Plate XXXI. figs. 2, 2 a.) 



Sponge compressed, triangular in outline, apparently supported on a short stem. 

 The walls, 3-8 mm. in thickness, run parallel with each other; their summit-margins 

 are rounded. On the compressed sides are two or three large ovate apertures. The 

 only example is 58 mm. in height and 50 mm. in width at the summit. 



The outer surface has numerous circular, irregularly disposed apertures, about 

 1 ram. in width. The thickness and spicular character of the dermal layer cannot 

 be determined owing to the condition of the specimen. The interior part of the 

 wall is formed of an apparently regular quadrate mesh ; the octahedral nodes are 

 •25 mm. apart. 



This species may be distinguished from D. heteromorphum by its different form and 

 the smaller dimensions of the mesh-interspaces of the interior of the wall. 



I have named this form after its discoverer, Mr. T. G. Bayfield of Norwich. 



Distribution. Upper Chalk: Norwich {coll. Bayfield). 



Genus SCLEEOKALIA, Hivde, n. g. 



Sponges cup- or nest-shaped, with very thick walls. Apparently free. The 

 interior surface of the cup is provided with circular or ovate canal-apertures disposed 

 in vertical rows. The exterior surface has no special canal-apertures. The canals 

 opening into the cloaca do not appear to extend far into the wall. A dermal layer, 

 composed of a thickened reticular mesh with irregular pores, forms the inner surface 

 of the wall ; the outer surface does not possess a special dermal layer. The sub- 

 stance of the wall is formed of a robust spicular mesh with octahedral nodes. Near 

 the iimer surface the mesh is very regularly disposed, but in the central and outer 

 portions of the wall the arrangement is of a less regular character. There does not 

 appear to be any definite boundary between the regular and irregular mesh ; and 

 the spicular rays are of the same thickness, and the nodes octahedral throughout 

 the wall. 



The type of this genus is an imperfect example of a nest-shaped sponge preserved 

 in a siliceous matrix. The structure of the interior of the wall has been partly 

 obliterated, so that the character of the canals cannot be ascertained with precision, 



u 



