STELLETTA. — THENEA. 25 



shaft, so that I do not know their length. These anchor-shaped spicules appear to 

 be rare in proportion to the other trifids. The surface of the sponge has not been 

 preserved, so that it is doubtful whether it was furnished with disks or stellates. 



The only specimen is from Sir P. Egerton's collection. 



Distribution. Upper Chalk : England. 



Genus GEODIA, Lam. 1816. 



Geodia'? clavata, Ilinde. 

 Geodia? clavata, Hinde, Foss. Sponge Sp. p. 29j t. 2. f. 1-5. 

 Relatively large, straight, trifid spicules, with short rounded knob-shaped head- 

 rays, either simple or compressed. The shaft constricted at the neck, and imme- 

 diately below slightly bulbous. Length varying from 7 to nearly 9 mm. ; greatest 

 width of shaft 0*585 mm. These spicules have only been found detached in the 

 interior of flints. 



Distribution. Upper Chalk : Horstead, Norfolk. 



Geodia] coeonata, Hinde. 

 Geodia coronata, Hinde, Foss. Sp. Sp. p. 31, t. 2. f. 6-8. 



Trifid spicules with small upright head-rays ; the shaft is swollen at the summit, 

 and gradually tapers to the extremity. Average length 4 mm.; width of shaft 

 0-45 mm. These spicules have only been met with detached in the interior 

 of flints. 



Distribution. Upper Chalk : Horstead, Norfolk ; Kent. 



GeodiaI Wrightii, Hinde. 

 1880. Geodia'^ Wrightii, Hinde, Foss. Sp. Sp. p. 31, t. 2. f. 12. 

 Trifid spicules with blunted head-rays projecting forwards from the head of the 

 shaft. Rays and shaft with ring-shaped expansions. Average length 2 mm. ; width 

 0"45 mm. At present they have only been found detached in the interior of flints. 



Distribution. Lower Green Sand : Haslemere, Surrey. Upper Chalk : Horstead, 

 Norfolk; South of England ; near Belfast (Jfr/<jf/i^); Coesfeld, Westphalia. 



Genus THENEA, Gray, 1867. 



Thenea, sp. 

 1880. Tisiphonia ? sp., Hinde, Foss. Sp. Sp. p. 43, t. 3. f. 16-23. 

 Trifid spicules with widely expanded, usually compound or bifurcate head-rays, 

 which are extended nearly at right angles to the shaft. The shaft varies greatly in 

 length in different specimens ; in some instances it is reduced to a mere rounded 



