lO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. QI 



STYLOSPIRA, n. gen. 



This genus is proposed for a sponge having no spicules other than 

 pecuHar spirally twisted styles. 



Genotype. — Stylospira tiioiia, new species. 



STYLOSPIRA MONA, n. sp. 



Holotype. — U.S.N.M. no. 22324; from station 38, latitude 18° 11' 

 55" N., longitude 67° 42' so" W. to latitude i8°io'N., longitude 67° 

 46' W., February 10, 1933, 240 to 260 fathoms. 



This specimen is doughnut-shaped, 1.5 by 3 by 3.5 cm, outside 

 measurements. The central hollow perhaps represents a place where 

 the sponge grew around some foreign material, which has since been 

 removed, and seems to have no physiological significance in the 

 sponge itself. The color is nearly white as preserved in alcohol, and 

 the consistency is difficult to describe inasmuch as it shows some 

 hard stony characteristics, but in other ways is compressible, almost 

 spongy. The surface is even and minutely punctiform. The apertures, 

 which are exceedingly minute, presumably represent pores, now 

 closed ; the oscules could not be located. The interior is minutely 

 cavernous, or " crumb-of-bread ", in structure. The spiculation as to 

 megascleres consists of large monaxons 20 /x by 500 z^, each bent 

 rather sharply near the blunt end. In fact, they are usually bent two 

 to four times, and most of them have at that end a swelling or tylote 

 modification, which is not always directly at the end, so that the spic- 

 ules may be regarded as styles that are partially tylote. The bends 

 are frequently so placed that the blunt end of the spicule is actually 

 spiral in shape. This is an unusual spicule type but is found, together 

 with rhabdostyles, in the sponge described as Microciona pusilla by 

 Carter (1876, p. 239). This should be transferred to the genus Rhab- 

 dosigma, whose genotype, Sigmaxinella mamniillata Whitelegge 

 (1907, p. 512), an Australian species, also has very similar mega- 

 scleres. Carter's specimen was from the West Indies, but R. mona 

 appears to have none of the peculiar sigmas characteristic of Rhab- 

 dosigma; instead it possesses raphides, about 2 /x by 150 /a in size, as 

 microscleres. With the possible exception of Rhabdosigma pusilla, 

 mentioned above, Stylospira mona seems to have no close relatives. 



RIDLEIA Dendy 

 RIDLEIA DENDIIA, n. sp. 



Holotype. — U.S.N.M. no. 22323; from station 38, latitude 18° 11' 

 55" N., longitude 67°42'5o" W. to latitude 18° 10' N., longitude 67° 

 46' W., February 10, 1933, 240 to 260 fathoms. 



