242 DR. mWDE AND MB. HOLMES ON SPONOE-KEMAINS 



they belonged. Smaller spicules of the same type also occur in 

 the recent Discodermia, Bocage. Detached spicules, similar to 

 figs. 2 and 3, are present in the ' Egeria' dredgiugs off the S.W. 

 coast of Australia at a depth of 2479 fathoms. 



PI. XIV. figs. 8, 9, 10, 11. Spicules in which the shafts are 

 much reduced or obsolete, and the heads are of thin siliceous 

 plates with rounded or slightly sinuous outlines. In fig. 8 there 

 is no trace of a shaft nor of axial canals, the border of the plate 

 is smooth and the central portion tuberculate ; in fig. 9 the sur- 

 face, with the exception of the outer border, is dotted over with 

 minute curved dimples, and there are three rudimentary canals; 

 in fig. 11 the canals are much longer than is usually the case 

 with these forms. The spicules are about '15 mm. in diameter. 

 Spicules of this type (with the exception of fig. 11) are present 

 in the dermal layer of the recent Discodermia, Bocage. 



Discodermia sinuosa, Carter. — PL XIV. fig. 12. Spicule with, 

 short shaft, head-plate fiat with margins deeply laciniate and 

 notched. Surface except near margins pitted over with small 

 depressions. Diameter "215 mm. Spicules similar to this form, 

 but somewhat smaller, are present in Discodermia sinuosa, Carter, 

 from the Grulf of Manaar (Ann. & Mag. Nat, Hist. s. 5, vol. vii. 

 1881, p. 372, pi. xviii. fig. 1 c, d). 



Dermal Spicules of undetermined Genus. 



PI. XIV. fig. 13. Spicule with short blunted shaft and hori- 

 zontally extended head, in which each of the normal three primary 

 rays subdivides into three subequal rays. The rays are sub- 

 cylindrical, tapering slightly and obtusely ended, and their sur- 

 faces are thickly covered with minute spines. Canals extend 

 into each ray and open at their extremities. Diameter across 

 head -091 mm., length of secondary rays '04 mm. 



PI. XIV. fig. 14. Spicule with straight, subcylindrical, obtusely 

 ended shaft, with two primary rays at the summit, each of w^iich 

 divides into three secondary rays. Only the base of the third 

 normal ray appears in this spicule. The rays are spined 

 the same as in the preceding form. Diameter across head 

 •081 mm., length of secondary rays '02 mm., length of shaft 

 •071 mm. 



This and the preceding (fig. 13) probably belong to the dermal 

 layer of a Lithistid sponge. In the trifurcate division of the 



