PORIFERA. III. 



IOI 



longest being often thin; the small styli have a length of 0-119— o - i6 mm and a diameter at the head of 

 o-02i mm . The large styli are generally in size nearest the greatest length, the shorter of them, which 

 are nearly intermediate between the large and the small, being rare. 2. The dermal spicules are 

 long and straight strongyla, sometimes one end, and sometimes both may be slightly swollen, in the 

 latter case the spicule approaching to a tylote; they are as a rule slightly polytylote. The length is 

 0-32 — 0-42 mm and the diameter 0-005— 0-007 mm . Some fine developmental stages were found which were 

 monactinal. b. Microsclera are of one form, sigmata, which are rather curious; they are large but 

 exceedingly thin, and they are more or less contorted up to a quarter of a turn, otherwise they are 

 of the common shape. The length is 0-084 — °' 12 mm ar >d the thickness o-ooi4 mm . The sigmata occur 

 through the whole tissue but are especially numerous at the surface. 



Locality: Station 9, 64 18' Lat. N., 27 00' Long. W., depth 295 fathoms; station 98, 65° 38' Lat. N., 

 26 27' Long. W., depth 138 fathoms. Both localities lie in the Denmark Strait. 



45. H. Dujardinii Bow. 

 PL X, Fig. 5. 



1866. Hymeniacidon Dujardinii Bowerbank, Mon. Brit. Spong. II, 224, 38. 



1867. Halisarca Dujardinii, Gray, Proc. Zool. Soc. 1867, 520. 



1874. Hymeniacidon Dujardinii Bowerbank, 1. c. Ill, 95. PL XXXVIII, figs. 1—4. 

 1882. Bowerbank, Norman, ibid. IV, 92, 48. 



1888. Dendoryx Dujardini, Topsent, Arch, de Zool. exp. et gen. 2, V bis, 115, PL VI, fig. 3, 12, 13 c. 



1890. — — , Topsent, Mem. de la Soc. Zool. de Fr. Ill, 201. 



1891. — — , Topsent, Arch, de Zool. exp. et gen. 2, IX, 528. 



1892. , Topsent, Resultats des camp, scient. du Prince de Monaco, Fasc. II, 99. 

 1892. Myxilla radiata Bow. Topsent, (partim, the last passage), ibid. 109. 



1894. Leptosia Dujardini, Topsent, Mem. de la Soc. Zool. de Fr., VII, yj. 



1896. — , Topsent, ibid. IX, 123. 



1896. — — . Topsent, Resultats scient. de la camp, du "Caudan", 275. 



1901. — — , Topsent, Arch, de Zool. exp. et gen. 3, IX, 353. 



1904. — , Topsent, Resultats des camp, scient. du Prince de Monaco, Fasc. XXV, 185, 



PL I, fig. 5- 

 1909. Hymedesmia Dujardinii, Luudbeck. Meddel. om Gronl. XXIX, 444. 



Tncrusting ; surface smooth; pore-sieves scattered on the surface. Spicula: megasclera; the 

 skeletal spicules acanthostyli with a globular, more or less marked head, spined in the zvhole length, 

 0-083 — o-22""", not divided into two groups; the dermal spicules subtylota to strongyla o-i^g — 0'28""". 

 No microsclera. 



Nearly all the specimens in my material of this species, and they are rather numerous, grow 

 as thin incrustations on the shells of a species of Valdheimia. and the specimens of the Valdheimia 

 were all living; one specimen grows on a mussel-shell, one on a Bryozoa, one on a stone with a speci- 

 men of Petrosia crassa and finally one on a Voeringia. Otherwise it is recorded as growing on stones, 



