PORIFERA. III. 



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

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

 placed on the imbedded material may 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. Megasclera. 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 cro2i 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 0-178 mm and the diameter of 

 the head is o-oiy" 1 . 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 O'596 mm and the diameter in the middle 0-005 o - on mm ; the 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 189192). 



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

 previously described species; these are: H.KoehleriTo^s.^ occultaBow., baculifcra Tops., crux O. Schmidt, 

 filifera 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, PI. XXI. figs. 17. 



- paupertas Bow. ibid., II, 223, III, PI. XXXV, fig. 48 (Hymeniacidori). 



1875. " vidua O. Schmidt. Jahresber. der Comm. zur wissensch. Unters. der deutsch. Meere in Kiel fur 

 187273, 120. (Spirasirella); Thiele, Arch, fur Naturgesch. 1903, I, 393, Taf. XXI, Fig. 27. 



1882. -- Peachii Bow. 1. c. IV, 64. PI. XIII, figs. 512. 



1885. -- mammilaris Frstdt. Kgl. Sv. Vetensk. Akad. Handl. 21, 6, 32, Tav. Ill, Fig. 3 a h. (Hastatus); 

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



1887. -- pustula Frstdt. Ofvers. Kgl. Vet Akad. Forh. 1887, No. i, 27, (Esparto). 



I 93- prostrata 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 Stylos fiction). 

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



fig. 3. (Hymeraphia). 



- Schmidti Tops, ibid., 189, PI. XV, fig. 9. (Leptosia). 



