28 THE VOYAGE OF H.M.S. CHALLENGER. 



distal half is ovate, and opens above by a short cylindrical proboscis (caminus). The 

 terminal mouth of the latter, or the osculum (o), is simple, circular, and has a diameter 

 of 0'5 mm. 



Longitudinal and transverse sections through the utricular sponge (figs. 1A, IB) show 

 that the internal cavity (or the gastral cavity) is perfectly simple, enclosed by a thin 

 wall of nearly equal thickness (about O'l mm.). This cavity opens above by the 

 distal ostium, and in the middle dilated portion by numerous small circular pores, 

 0'03 to - 04 mm. in diameter (p). The pores seem to be absent in the basal pedicle as 

 well as in the distal proboscis. Probably the sea-water enters into the gastral cavity by 

 these dermal pores and issues by the distal osculum (o). 



The thin and rather firm wall of the utricle is mainly composed of siliceous Eadio- 

 larian tests of those wonderful and most elegant forms making up the Eadiolarian 

 ooze of Station 271. They are connected by a granular maltha, or the ground-mass of 

 the connective tissue, which constitutes the outer wall of the sponge. Through this 

 maltha are scattered numerous very small stellate cells, and a few larger amoeboid 

 wandering cells («) ; these are more distinct in the thinner walled proboscis, which is 

 free from xenophya. In some transverse sections (fig. IB), through the inferior part of 

 the gastral cavity, close to the pedicle, there appear between the xenophya and within 

 the maltha (m) single eggs (e), naked amoeboid cells, O'l to 0"2 mm. in diameter. Their 

 nucleus or germinal vesicle (v) includes a distinct nucleolus. Further, in some of these 

 sections are visible, on the inside of the wall, small thin bands composed of small 

 granular cells («.); these are probably the remnants of the flagellated entodermal 

 epithelium. Fig. lC shows a small portion of the wall, seen from the inside, in which 

 the above-mentioned structures are more or less distinct. 



Ammolijnthus Jmliphysema, n. sp. (PI. VIII. fig. 2). 



Habitat. — Central Pacific, Station 270; September 4, 1875; lat. 2° 34' N., long. 

 149° 9' W.; depth, 2925 fathoms; bottom, Globigerina ooze. 



Sponge ovate, with a simple osculum at the distal end, arising from a slender 

 cylindrical pedicle, which is fixed by a broad basal plate. Pseudo-skeleton composed of 

 calcareous shells of Foraminifera. 



Ammolynthus haliphysema is closely allied to the preceding species, but differs from 

 it in the simple, not proboscidial, opening of the osculum (o), and principally in the com- 

 position of the pseudo-skeleton, which is built up of calcareous shells from the Globigerina 

 ooze. The ovate body of the sponge is much larger, 5 to 8 mm. in diameter, and arises 

 from a slender, cylindrical, slightly curved pedicle, which is 10 to 12 mm. long and 1 

 to 1*2 mm. broad. This is broadened below and attached to the bottom on the proximal 



