MK. S. O. RIDLEY ON THE GENUS DIRRHOPALUM. 479 



point ; bent, but not so sharply as in Schmidt's figure 176 ; size 

 0*99 by '06334 millim. (3) Dumbbell or double-headed, curved, 

 cylindrical spicule ; size *479 by -06334 millim. 



Flesh- spicules of two kinds: — (1) Tricurvate acerate, bow- 

 shaped, tapering gradually from centre to sharp points ; size 

 "082 by -003167 millim. (2) Equianchorate, bipalmate, the palms 

 with squarely truncate proximal margins, shaft almost straight ; 

 length about "019 millim. 



2. DlRRHOPALUM ? CLOPETARIUM. 



Plocamia clopetaria, Schmidt, I. c. p. 63, pi. iv. fig. 18. 



Consisting of a basal lamina, in which the dumbbell spicules 

 and a peculiar pegtop-like form (4) are united by ceratinous 

 material (polarizing light) and sarcode, and of spicular tufts 

 rising from this lamina, and consisting each of a very large 

 basally-spined acuate (1) surrounded by a considerable number 

 of small spicules (2) of a similar kind ; the bases of the spicules 

 in the tuft are united by ceratinous material. 



It is possible that the points of the peculiar form (4) feebly 

 echinate the basal lamina. In any case they cannot be varieties 

 of the dumbbell spicule, as stated by Schmidt (I. c), for no 

 transition forms occur in the same preparation, and their inde- 

 pendent existence in the fossil state is undoubted (see p. 486). 



Skeleton-spicules of four forms : — (1) Large, curved acuate, 

 the base finely tuberculate ; length (none were found entire) pro- 

 bably about 1"8 millim., thickness "057 millim. (2) Small, 

 straight acuate, basally spined, slightly constricted just above 

 base ; size '29 by '01108 millim. (3) Dumbbell spicule, curved so 

 as to form about a third part of a circle, coarsely tuberculate in 

 approximately verticillate whorls on shaft, evenly so over the ends ; 

 both ends and centre of shaft inflated to the same diameter ; size 

 •152 millim. long, inflated ends and centre '05067 millim. thick. 

 (4) Short, rapidly tapering acuate (" pegtop "-shaped spicule), 

 coarsely tuberculate ; one sixth of the apical end is almost smooth, 

 becomes more rapidly narrow than the rest, and is traversed to 

 its extremity by the central canal ; size '1647 by '076 millim. 



Flesh- spicules. — JSTone were found after careful search in the 

 mounting (which, however, is small) in the Museum collection, 

 unless tricurvates are represented by a single specimen of a fine 

 barely tricurvate acerate ; size '108 by '003167 millim. 



Obs. If the flesh-spicules should really be wanting, this species 



