REPORT ON THE MONAXONIDA. 7 



Spicules. — Large, straight, or very slightly curved, fusiform oxea (PL II. fig. 1), 

 sharply and usually gradually pointed. Size commonly about 0'7 by 0'022 mm., but 

 often much larger, measuring about 1'25 by 0"031 mm. In these larger spicules one end 

 is usually markedly larger than the other, and the points are irregular. 



This is a very interesting species, and forms another example of the extraordinary 

 diversity and richness of the sponge-fauna at Station 320. We have called the species 

 " latrxinculioides" owing to the curious resemblance which it bears in external form to 

 species of the genus Latrunculia, of which two were obtained from the same Station. 



As we have already had occasion to remark, the most noteworthy character of the 

 species is the arrangement of the pores in definite, raised pore-areas. We at first 

 thought that this feature would prove of generic importance, but concluded finally that 

 it is not so, being apparently only a case of adaptation, which, however, at once 

 separates the species from all others of the genus. The arrangement of the pores is, as 

 usual, closely correlated with the arrangement of the dermal skeleton. The dermal 

 skeleton in this sponge is so closely packed together that there is literally no space left 

 for the pores {vide PI. XLVI. fig. 5), hence these are almost entirely confined to special 

 areas set apart on purpose for them (PI. I. figs. 5, 5a). It is very interesting to notice 

 how precisely the same adaptation in the arrangement of the pores has taken place in a 

 totally diS'erent and widely separated sponge, viz., Latruncidia cqnccdis (vide infra); 

 here also the dermal skeleton, although of quite a difi"erent kind, is so dense as to 

 allow no room for the pores, which are confined to special raised areas. It is further 

 interesting to notice how these two sponges consequently resemble one another in 

 external form, and that both were obtained from the same station. 



Locality. — Station 320, February 14, 1876 ; lat. 37° 17' S., long. 53° 52' W. ; off' 

 the mouth of the Rio de la Plata; depth, 600 fathoms; bottom, green sand; bottom 

 temperature, 37°"2. Three specimens. 



" Halichondria sp. (a). 



Under this head we must mention two amorphous masses of sponge, apparently 

 belonging to the genus Halichondria, each encrusting a delicately branched white 

 Gorgonia from Station 320. The specimens do not present sufficient characters to 

 make a specific determination desirable. They are very soft, spongy, and cavernous, 

 and the skeleton is confused and lax in the extreme. Spicules, smooth, slightly 

 curved oxea, rather abruptly pointed at each end ; size, very fairly constant, about 

 0-35 by 0-017 mm. 



Locality. — Station 320, February 14, 1876; lat. 37° 17' S., long. 53° 52' W.; off 

 the mouth of the Rio de la Plata; depth, 600 fathoms; bottom, green sand; bottom 

 temperature, 37°'2. Two specimens. 



