PORIFERA. III. in 



sponge and partly on the imbedded foreign particles, such as large sponge-spieules, gravel and the like, 

 which particles must be considered therefore also as substratum for the sponge; the acanthostyli 

 placed on the imbedded material ma}' point in every direction, and the main skeleton is, according to 

 the manner of growth of the sponge, quite irregular. At the head of each acanthostyle there is a 

 small, but distinctly observable amount of spongin. 



Spicula: a. Mcgasclera. i. The skeletal spicules are acanthostyli, divided into two groups, 

 large and small; the large styli are straight or slightly curved near the base; the head is very small 

 or almost quite absent, the basal part has some small or moderately sized spines, but only for a 

 short distance, the remainder of the shaft being smooth or slightly and imperceptibly gritty. The 

 length is 0-40 — o-65 mm and the diameter at the base 0-017— o-02i mm . The small acanthostyli are 

 generally straight with a slight but distinct head-swelling; they are densely spined in the whole 

 length, the spines on the head being the largest The length is 0-14— o-i78 mm and the diameter of 

 the head is 0-017 mm . 2. The dermal spicules are tornota but of a characteristic shape; one end is 

 pointed in the way common for tornota and not very short, the other end is shorter and more roundish 

 pointed and has a very distinct mucro; the latter end is somewhat thicker than the former; the 

 tornota are long, straight or nearly so and slightly thicker in the middle than towards the ends. 

 The length is 0-38— 0-596"™ and the diameter in the middle 0-005 —o-oi 1 ram ; tne intermediate sizes are 

 by far the most common. Microsclera are not present. 



Locality: At East Greenland, 70° 32' Lat. N., 8° 10' Long. W., depth 470 fathoms (The Ryder 

 Expedition 1891—92). 



Above I have described 51 species of Hymedesmia of which only seven are determined as 

 previously described species; these are: H. Koehlcri Tops., occulta Bow., baculifera Tops., crux O. Schmidt, 

 fili/era O. Schmidt, mucronata Tops., and Dujardinii Bow. I have tried to find out the other previously 

 described species, and I think that at all events most of them are enumerated in the following list: 



1866. H. zetlandica Bow. Mon. Brit. Spong. II, 152, III, PL XXI. figs. 1—7. 



« — paupertas Bow. ibid., II, 223, III, PI. XXXV, fig. 4—8 (Hymeniacidou). 

 1875. — vidua O. Schmidt. Jahresber. der Comm. zur wissensch. Unters. der deutsch. Meere in Kiel fiir 



1872—73, 120. (Spirastrella); Thiele, Arch, fiir Naturgesch. 1903, I, 393, Taf. XXI, Fig. 27. 

 1882. — Peachii Bow. 1. c. IV, 64. PI. XIII, figs. 5-12. 

 1885. — ma mm 1 la r is Frstdt. Kgl. Sv. Vetensk. Akad. Handl. 21, 6, 32, Tav. Ill, Fig. 3 a— h. (Nastatus); 



Thiele, Arch, fiir Naturgesch. 1903, I, 389, Taf. XXI, Fig. 22 a— d. 

 18S7. — pustula Frstdt. Ofvers. Kgl. Vet. Akad. Forh. 1887, No. 1, 27, (Espcria). 



1903. — prostrala Thiele, Abhandl. Senckenb. nat. Gesell. XXV, 955, Taf. XXVIII, Fig. 20. 



— norvegica Thiele, Arch, fiir Naturgesch. 1903, 1, 390, Taf. XXI, Fig. 23 a— c. (perhaps a Stylostichon). 



1904. — mutabilis Tops. Resultats des camp, scient. du Prince de Monaco, Fasc. XXV, 166, PI. XIV, 



fig. 3. {Hymeraphia). 

 « — Schmidti Tops, ibid., 1S9, PI. XV, fig. 9. (Lrptos/a). 



