THE SPONGES. 27 



from ^ nearly to | total length ; shaft with a few scattered tuberosities, 

 and frequently but not always with a ring of tuberosities at the middle. 

 The umbel is often evenly rounded, as in Fig. 15, but as frequently some- 

 what truncated at the poles and flattened along the sides, as in Fig. 14. 

 These spicules, which owing to their size may be regarded as a third type 

 of macramphidisc, pass through intermediate stages into very similar 

 mesamphidiscs, 60-80 fj. long, in which the umbel depth somewhat 



exceeds ^ the total length. The mesamphidiscs are connected by 



transitional forms with micramphidiscs, 18-20 jx long, of the character 

 usual in ILjalonema. 



The skeletal resemblances to //. bianchoratiim are extensive and close. 

 The only important point of difference is afforded by the third t3-pe 

 of macramphidisc, which might properly be designated as an enlarged 

 mesamphidisc, since it is connected by an unbroken series with the latter. 



Hyalonema 3. 



Station 3414' Three fragments, all including the lower end of the 

 sponge with the root tuft. 



The largest piece is a laterally compressed triangular mass 45 mm. 

 wide by 50 mm. high. The root tuft where it adjoins the sponge is 5 mm. 

 thick, and includes about 25 spicules varying in thickness from 200 /x to 

 730 /x. The spicules are all broken off below, the fragment of root tuft 

 measuring 100 mm. in length. The tuft bears no anemone. At the base 

 of the body there is a conspicuous firm and dense collar-pad surrounding 

 the root spicules. The other two fragments are likewise laterally com- 

 pressed triangular masses, but from smaller sponges. The upper diameter 

 of the root tufts is something less than 2 mm., and the spicules do not 

 exceed 250 /a in thickness. Again the lower ends are all broken off, 

 although the tuft in one case is 200 mm. long. Both tufts at the upper 

 end are surrounded by small Pahjtlioa colonies, each including two indi- 

 viduals. In these specimens the basal collar-pad has not developed. It 



is noteworthy that in all three specimens the lower end of the sponge 

 body has a triangular outline, and is laterally compressed to a marked 

 degree. 



The surface is so injured that it is not possible to reach a conclu- 

 sion as to the character of the dermal pinuli. The micro-oxyhexacts, 



which are abundantly scattered throughout the parenchyma, are small 

 slender forms (Fig. 12, Plate 2) with rays 30-36 /x long by 2 /x at the 



