HEXACTINELLIDA. 21 



without hypodermal pentactins. Auiochone, which has an everted gastral surface, 

 differs from the new genus in being stalked, and in possessing only one kind of 

 discohexaster.* 



Anaulosoma schulzii. 



(Plate III., figs. 5, 6, and Plate V., fig. 2 a-m). 



Sponge shaped somewhat like a molar tooth, with rounded or carinated mammillge 

 at the lower end, and with a free gastral surface at the upper end. Surface smooth, 

 without pleuralia, with a few diactin marginalia at the junction of the dermal and 

 gastral surfaces. With a few very small tufts of diactin basalia extending downwards 

 from the mammillae. Principalia, bundles of diactins, also hexactins, pentactins, 

 stauractins, and tauactins. Autodermalia, pentactins ; hypodermalia diactins in bundles 

 forming a network. Autogastralia, pentactins, with a few hexactins. 



There are two specimens (A, C) and two fragments (B, D) of this sponge. 

 Specimen A (III., 5), the type, from McMurdo Bay, is 6-5 cm. in height, 4'5 cm. in 

 width, and 3-3 cm. in thickness. The texture of the sponge is loose. The thin felt-like 

 gastral surface, with several thin-edged exhalant orifices, is easily distinguishable from 

 the lace- like dermal surface, the two being separated by a sharp edge. The oval gastral 

 .surface, 5x3 cm., which occupies the whole upper end of the sponge, slopes down- 

 wards a little ; the largest of the " oscules " is oval, and 1 x • 5 cm. in diameter ; 

 the walls of the large canal into which it leads are lined simply with scattered 

 canalaria in the form of oxyhexasters. The autogastralia are pentactins, and rarely 

 hexactins. Two or three deeply curved diactins are present on or near the gastral 

 margin, but it is doubtful whether they are really marginalia, or, indeed, whether they 

 belong to the specimen at all. The lower end of the sponge is prolonged into two 

 rounded extensions, each with a small tuft of basalia. 



The small specimen C (III. 6) is somewhat wedge-shaped, the inferior end 

 narrowing to a ridge, with a small tuft of basalia projecting obliquely downwards and 

 outwards from only one of the ends of the ridge. The upper end, or gastral surface, 

 1 • 1 cm. in diameter, is in the form of a small circular area, with one small circular 

 orifice (1'5 mm. in diameter) of an exhalant canal. Round the margin is a circle of 

 small diactin marginalia projecting about 6 mm. The two fragments (B, D) are the 

 lower halves of broken specimens ; in them the broken surface shows the openings of 

 numerous canals passing vertically upwards from the base. 



In Anaulosoma schulzii there is a marked difference in the appearance of the 

 dermal and gastral surfaces, the former showing a fine lace-like reticulum perceptible to 

 the naked eye, while the latter has an opaque, felt-like appearance. This difference is 

 chiefly due to the arrangement of the hypodermal skeleton. In the dermal region 



* I have recently fottnd miorodiscohexasters in Auiochone (Crateromorpha) lankesteri Kirkp. from South 

 Africa. These spicules escaped my notice when I first described the sponge (Ann. Mag. N.H. (7) VII., 1901, 

 p. 457). 



2 K 2 



