122 FARREA OCCA SCUTELLA. 



They are on the whole cyhndroconic, about 9 fx thick at the base, and attenuated 

 distally to 4-6 n. The end is rounded off. Frequently a slight thickening is 

 observed just before the end. The lateral rays are spiny. On the basal and 

 middle-jjart of the rays the spines are 2-4 ^ high and arise vertically ; on the end- 

 part they are 1-1.5 n high and obliquely inclined towards the end of the ray. 

 The spines of the lateral rays are larger in the dermal pentactines than in the 

 gastral. In the former they are larger and much more numerous on the outer 

 side of the rays than elsewhere, the inner side being often nearly destitute of spines. 

 On the lateral rays of the gastral pentactines the concentration of spines on the 

 outer side is not so pronounced. The axial thread traverses the lateral rays 

 quite to their ends. The proximal ray is straight, 180-260 m long, and usually 

 bears only small spines near the end. In most of the pentactines, particularly 

 the dermal ones, a rudiment of the sixth distal ray is present. This is 14-17 ix 

 long, and as thick as the other rays. It bears a few large, upwardly directed 

 spines. Sometimes only a single terminal spine is present. In this case the 

 distal ray (together with the spine) appears a sharp-pointed, conic thorn. 



The uncinates are very rare and I cannot positively assert that those ob- 

 served in the preparations really belong to the sponge. An intact one was 

 straight, pointed at both ends, and measured 1.6 mm. long and 10 ^ thick near 

 the middle. Its spines were slender and 8 ^ long. 



The oxyhexasters (Plate 26, figs. 1-7, 8c; Plate 27, fig. 6c) are 105-140 /x in 

 total diameter. Their main-rays enclose angles of 90° with each other and are, 

 in the same spicule, usually equal ; sometimes, however, considerable inequalities 

 are observed in them, the proportion of the length of the shortest to that of the 

 longest sometimes being 3:5. The main-rays are 22-37 /x long, straight, cyhn- 

 droconic, 2.8-3.8 IX thick at the base, and attenuated distally to 2-2.7 /x. They 

 are perfectly smooth and traversed by an axial thread, which terminates below 

 the end and does not give off branches for the end-rays. Of end-rays there are 

 one to four, usually two or three. The end-rays are slightly curved. Concave to 

 the continuation of the main-ray at the base, and farther on usually fairly straight, 

 rarely considerably and irregularly curved. They are conic, uniformly attenu- 

 ated to a fine point, 30-44 ii long, 1.3-2.2 ij. thick at the base, destitute of axial 

 threads, and, like the main-rays, perfectly smooth. When only one end-ray is 

 present, it extends in the continuation of the axis of the main-ray to which it 

 belongs. When there are two they usually enclose an angle of about 60° and lie 

 in or near a plane which passes through the main-ray from which they arise. 

 The planes in which such end-rays extend are usually oblique to the two axial 



