POLTJEREA.— BOLOSPONGIA. 73 



Genus POLYJEREA, Fromentel emend. Zittel. 



PoLTJEREA ARBUSCULA, Ilinde, n. sp. (Plate XVI. figs, 2, 2 a.) 



Sponge massive, growing from a simple, compressed stem*, from which spring 

 upright, straight, or slightly curved, cylindrical, compressed, or club-shaped branches, 

 which also subdivide. The branches are mostly separate, but occasionally coalesce 

 together ; they average 36 mm. in thickness. At the summit of the branches are the 

 apertures of numerous canals, about 2 mm. in width, which extend vertically down 

 the branches. The lateral surfaces are covered with smaller apertures of canals, 

 1 mm. in width, which extend towards the centre, of the branch. 



The spicules of the interior mesh have smooth arms and prominent nodes. 

 Occasionally traces of the dermal layer are preserved ; it consisted, in part at least, 

 of trifid spicules, with horizontal heads of pointed rays, similar to those of Nelumbia 

 tuherosa. 



I am unable to determine how far this species differs from Polyjerea ramifera, 

 Zitt.*, in its mode of growth. By the form and disposition of the branches it may 

 readily be distinguished from Polyjerea gregaria, Mich.f sp. 



Distribution. Upper Green Sand : Warminster. Grey Chalk : near Dover. 



PoLTJEREA LOBATA, Hinde, n. sp. (Plate XVI. fig. 3.) 

 Sponge consisting of a compact group of fig- or barrel-shaped, or occasionally 

 cylindrical individuals, growing from a flattened base or from a slight peduncle. 

 The outer surface of the group is partially lobed, but in the central portion the 

 individuals are closely amalgamated together ; the summits are, however, free. The 

 number of individuals in each compound mass varies between six and twenty. In size 

 the compound form is from 90 to 105 mm. in width, and about 64 mm. in height. 



The summit of each individual is truncate, or has a slight shallow depression ; the 

 canals opening at the summit are 2 mm. in width, and extend nearly to the base of 

 the sponge. The spicules of the interior mesh have been replaced by calcite in the 

 specimens from the Grey Chalk ; in the forms from the Upper Green Sand they have 

 relatively short, smooth arms and prominent junction-nodes. Only traces of a dermal 

 layer have been preserved ; it resembles in the form of its larger spicules that of the 

 last species. 



Distribution. Upper Green Sand : Warminster. Grey Chalk : near Dover. 



Genus BOLOSPONGIA, Hinde, n. g. 



Sponges subspherical or elongate and lobate. No regular series of canals is 

 present ; in the rounded forms there are interior loculi which communicate with the 

 • Studien, II Ab. p. 83. t Icon. Zooph. p. 134, t. 38. f. 1. 



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