On a Badiolarian, &c. By Prof. P. Martin Duncan 111 



and is a much more complicated body than the others, resembling 

 in its body-structure, but not in the long spiculate arrangement, a 

 full-grown Holtenia. 



Description : — 



The body is not quite 3 mm. in breadth, and is less in 

 height ; it is broadly cup-shaped, with a large oscule whose limits 

 are ill defined. There are two portions to be considered : the main 

 framework, and the outer dermal framework. 



The main framework is composed of a series of large quinque- 

 radiate spiculse, four of the radii being on one plane — that of the 

 surface of the sponge — and the other at right angles, and pene- 

 trating inwards towards the centre. The outer radii are faintly 

 curved, are equal, and taper to their extremities. 



Where they join to unite with the long attenuate inner part, 

 there is scarcely any swelling, or none at all externally. The 

 rays of one of these four-armed spiculsB nearly reach to the 

 centres of their neighbours, but there is never perfect and solid 

 contact. These primary spiculse are not all of the same size, 

 the largest being nearly twice the size of the others. These 

 smaller ones are overlapped by the others. Below the trellis-work 

 formed by the curved radii, is the thickness of the sponge- body, and 

 it is composed of the long, needle-shaped inner limbs of the primary 

 spiculse, and amongst them are hexradiate spicules with the junction 

 of the cross-pieces smaller, and the radii are shorter than the ver- 

 tical portion. Besides, there are long, slender, slightly curved, 

 attenuate pointed spiculse, without hooks or ornamentation. 



These three kinds of spicules are especially those of the body, 

 and there are numerous long, linear, delicate spiculae, plain at the 

 ends, which come from the body-mass and pass out through the 

 lattice-work of the great quinqueradiate spiculae, and bend over the 

 framework and enter partly into the composition of the derm. 



The spiculse. of the derm are numerous, and are of six 

 kinds : — 



Small quinqueradiate spiculae, whose four limbs rest partly on 

 the outer part of the primary spicules of the body, and the fifth 

 passes inwards. 



Small quadriradiate spicule, with their attenuate extremities 

 minutely punctate. 



Small hexradiate spiculse, with minutely punctate extremities. 



Small feather spiculae, the feather being excessively slender, yet 

 sharply aculeate, in irregular whorls ; and the four other equal 

 Hmbs being in the form of a cross, resting in the derm. 



Small hexactinellid spiculae, with feathered ends like the last. 



Long, slender, attenuate, linear spiculae, some continued within 

 the body, others free and curved about the derm. 



The projections from the surface are the numerous minute 



