fi 



22 



THE SPONGES. 



abundant in the walls of some of the canals, and are scattered in the 

 parenchyma. The shaft bears small, scattered, irregular tubercles, often 

 a circle of tubercles, in the middle. The umbel has a deep bell shape, and 

 is more than J the total length of the spicule. The umbel rays are 8 in 

 number, long, narrow, and pointed. A typical spicule has the following 

 measurements: total length, 60 ft; length of umbel, 24 jx; width of umbel, 

 20 /x. The total length of the spicule varies from 40 to 65 /x. 



Micramphidiscs of the common Hyalonema type, 25 to 30 jit long, 

 are fairly common in the parenchyma. Transitional forms between these 

 and the mesamphidiscs are easily found. 



The skeletal resemblances between this species and Hyalonema bian- 

 choratum, sp. nov., are striking, involving as they do the characteristic 

 spicules, macramphidiscs, dermal pinules, and oxyhexacts (comp. Plate 2, 

 Figs. 2, 5, 10, and 11). Nevertheless the form of body is very different 



in II. bianchoratum there are two types of 



macramphidisc. Moreover, the macramphidisc of II pedunculatum never 



_ * 



assumes the shape with truncated poles and flattened sides which is 

 common in II. bianchoratum (Plate 2, Fig. 1). The resemblance is 

 thus only partial, although close in the parts concerned. 



in the two species, and 



/ 





r. 



Hyalonema bianchoratum, sp. nov. 



Plate 2, Figs. 1-11. 



Diagnosis. Body cup-shaped with deep gastral cavity. Numerous efferent canals open 

 independently on the gastral surface ; their apertures covered in by the gastral membrane. 

 Micro-oxyhexacts with minutely denticulate rays about 50 /x x 4 ^ ; rays commonly 

 slightly curved or straight. Dermal and gastral pinuli are alike, and pentacts ; distal 



* 



ray 250-530 /x long, comparatively stout, with long appressed upper spines and outwardly 

 projecting lower spines, with a terminal cone. Macramphidiscs of two types. In one 

 type the umbel is | to -§- total length, with acutely pointed rays; umbel width greater 

 than its depth ; total length about 450 /x. In the other type umbels closely approach 

 equator of spicule ; rays rounded at the end ; umbel wider than deep ; total length, 

 150 /x-250 /x. 



Station 3415, one specimen. 



Sponge body (Plate 2, Fig. 6) is cup-shaped and, possibly owing to 

 packing, is laterally compressed. The entire cup is 50 mm. deep, and has 

 a greatest width of 75 mm. The cavity of the cup is 30 mm. deep, and 

 the wall about 12 mm. thick. The wall thins away toward the free edge, 

 but a marginal fringe separating the inner or gastral surface from the outer 



