CALYCOSILVA CANTHARELLUS. 75 
have been observed. The lateral rays of these spicules extend paratangentially 
like those of the larger ones, but are, apart from this, more or less irregularly 
disposed and lie anyhow in the meshes of the quadratic network formed by the 
lateral rays of the large pentactines. 
In most of the pentactines the apical ray is well-developed, longer than the 
lateral rays; in some it is reduced and considerably shorter than the laterals. 
The pentactines with short apical ray appear to be scattered indiscriminately 
among the pentactines with long apical ray. 
Most of the apical (proximal) rays of the pentactines penetrate and extend 
beyond the paratangential membranes or networks forming the floors of the sub- 
dermal and subgastral cavities. The end-part of many transverse rhabds are 
parallel to and in close contact with proximal pentactine rays (Plate 2, fig. 12b). 
The microhexactines are very rare and have been found only in the regions 
of the subdermal and subgastral cavities. 
The regular onychhexasters are abundant in the choanosome and in the 
floors of the subdermal and subgastral cavities (Plate 2, fig. 3; Plate 5, fig. 1). 
Some also occur in the proximal parts of the columns and threads which traverse 
these cavities. They are not confined to the body proper of the sponge and also 
occur in the stalk. These onychhexasters form a series, one end of which is 
represented by onychhexasters with short and stout end-rays, the other by 
onychhexasters with long and slender end-rays. The former are found in the 
proximal parts of the subdermal and subgastral regions of C. c. vars. simplex 
and helix, but appear to be absent in C. c. var. megonychia. The latter are, 
in all varieties, plentiful in the interior. Intermediate forms are met with 
wherever onychhexasters occur. 
The oxyhexasters occur in small numbers in the choanosome of C. c. var. 
helix and somewhat more frequently in C. c. var. megonychia. 
The helonychhexasters, which occur only in C. c. var. helix, are met with 
in fairly large numbers in the floors of the subdermal and subgastral cavities 
and are also found in the proximal parts of the columns and threads traversing 
these cavities. These spicules are not uniformly distributed throughout. this 
region, but in some parts of it are much more numerous than in others. 
The plumicomes are confined to the columns and threads which traverse 
the subdermal and subgastral cavities and are more numerous in their distal 
than in their proximal parts. Their paratangential distribution is fairly uni- 
form. They are quite abundant in C. ¢. vars. simplex and helix, but very rare 
in C. c. var. megonychia. 
