44 Ji. KIKKl'ATincK. 



HoPLAKlTHAHA Kiikpatrick.* 



1907. ffopMi/hara Kirkpatrick (10a. p. 285). 



Mycaliuae possessing exotylcs with large spherical spined heads, and with fim- 

 briated pLicocheles. 



HOPLAKITHARA DENDYI. 



(Plate XIX., figs. 6, 6a, Gl), and Plate XXIII., fig. 6a-c-.) 

 1907. Hoplahitluira dendiji Kirkpatrick (10a, p. 28G). 



Sponge ill form of a .small (iushion, attached by a narrow base. Surface smooth 

 to the naked eye. Colour, pale l)rowii in spirit. Consistence, liard externally, soft 

 within. Flagellated chambers 32*5m in diameter, .spheroidal, eurypylous. 



Skeleton with protective armour formed l)y gigantic spheroidal heads of exotyles, 

 the exotyles being arranged as radiating bundles in form of inverted cones, with the 

 apices a little below the cortex ; with scattered strongyle.s. 



Spicules. Megascleres. Exotyles f with the heads a little inclined to the 

 long axis of the spicule, the proximal end (in tlie interior of the sponge) rounded, the 

 distal end swollen into large spherical heads, with short cylindrical .spines covering the 

 distal three-fourths of the head. Total length 358 /«, the shaft enlarging in diameter 

 from 6" 5 m at the proximal end to 16/u just below the head. Head, 55 m in diameter; 

 cylindrical denticles, 1 • 76 to .3 ■52 m in height, with finely denticulate edge, and with 

 cup-like depression at the summit. 



Strongyles straight, fusiform, smooth, 467'5m long, 9 ■75m in diameter at centre, 

 6 ■ 5 M in diameter at ends. 



Micro.scleres. Placocheles, fimbriated, 84^5 m long, 29 ■25 m broad; length of 

 tooth, 37 • 75 M. 



Sigmata very small, slender, C-shaped, 8 • 8 m long, 5 '28 m broad, • 9 m thick. 



The minute .spheroidal or cushion-shaped specimen was 2'2 mm. in height and 

 3 mm. in horizontal diameter ; it was growing on the side of an Alcyonarian, creeping 

 over a l)ranc]ied CclU'pora. No pores or oscules were discernible. The under surface, 

 which was narrowed to the point of attachment, was paler in colour than the upper. 



The new genus is closely related to the Mycaline genera Rliaplddotlieca and 

 Guitarra, to the former by its exotyles, and to the latter by its fimbriated placocheles. 



The distal knolts of the exotyles of B. mais/iall-halUi Kent, 49 m in diameter, are 

 smooth and spherical, and those of i?. rhopalophora Schmidt {R. qffinis Carter, 6Y^e Thiele 

 22. p. 383) are 104 m long and 30 m broad and club-.shapcd. Lundbeck (13. p. 32) 

 regards these two .species as probably identical, and certainly the difterences are slight. 



In the centre of the heads of the exotylcs of J/, deitdyi is an oval granular zone, 

 whicli at first suggests a cavity filled with protoplasm, but that there is no cavity is 



* oTrXn ([)1. of oTrXof), ariiiour ; kiBujui, a giiitar. 



t Professor Dontly, to whom I showed these veiiiarkable exotyles with tlieii- large sjiincd heads, regarded them 

 as possible examples of spicules whieh miglit fonii a surface layer of pseudasters by reduction of the shafts. 



