ago DISCOVERY REPORTS 



I.paiipcra, Parfitt, 1868, p. 8 ; /. iinijormis, Bowerbank, 1874, p. 139, pi. Iv, figs. 8-10 ; /. normani, 

 id., loc. cit., p. 141 , pi. Ivi, figs. 1-5 ; /. clarkei, id., he. cit., p. 142, pi. Ivi, figs. 1 1-15 ; I.fucorum, 

 id., loc. cit., p. 142, pi. Ivi, figs. 16-19; I- alderi, id., loc. cit., p. 143, pl. Ivi, figs. 20-26; /. ed- 

 wardii, id., loc. cit., p. 148, pl. Iviii, figs. 15-18 ; /. gracilis, id., loc. cit., p. 149, pl. Iviii, figs. 23- 

 26; /. imitata, id., he. cit., p. 223, pl. Ixxvi, figs. 3-6; /. invalida, id., loc. cit., p. 285, pl. Ixxxv, 

 figs. 8-10; /. dubia, id., he. cit., p. 323, pl. xc, figs. 4-7; Hymeniacidon ealhsus, Bowerbank, 

 1882, p. 86, pl. iv, figs. 6-8; Amphihetus gracilis, Vosmaer, 1880, p. iii; A. compressus, 

 id., he. cit., p. 112; A. dubius, id., he. cit., p. 112; A. imitatus, id., loc. cit., p. 116; A.fucorum, 

 id., loc. cit., p. 117; A. normani, id., he. cit., p. 117; A. clarkei, id., loc. cit., p. 119; Isodictya 

 gracilis, Bowerbank, 1882, p. 136 ; /. invalida, id., he. cit., p. 136 ; /. normani, id., loc. cit., p. 136 ; 

 /. hispida, id., loc. cit., p. 136, pl. xii, figs. 1-5; /. alderi, id., loc. cit., p. 138; /. edzvardii, id., 

 loc. cit., p. 138; I.fucorum, id., loc. cit., p. 138; /. clarkei, id., loc. cit., p. 139; /. paupera, id., 

 loc. cit., p. 139; /. uniformis, id., loc. cit., p. 139; /. dubia, id., he. cit., p. 140; /. imitata, id., 

 loc. cit., p. 141 ; /. involuta, id., he. cit., p. 143, pl. x, figs. 1-4; /. pertenuis, id., he. cit., p. 144, 

 pl. xiii, figs. 1-4; /. seitula, id., loc. cit., p. 146, pl. iv, figs. 1-3, pl. ix, figs. 1-3 ; Esperia normani, 

 Fristedt, 1885, p. 42; Reniera fucorum , Topsent, 1888, p. 148; R. paupera, id., loc. cit., p. 148; 

 R. uniformis, id., loc. cit., p. 149; Stylinos uniformis, id., 1891, p. 535; Esperiopsis normani, 

 Lundbeck, 1905, p. 13, pl. viii, fig. 2; Esperiopsis sp., id., loc. eit., p. 15, pl. viii, fig. 3; E. ed- 

 zvardii, Thiele, 1905, p. 441 ; E. fucorum, Stephens, 1912, p. 36; E. edzvardii, Hentschel, 1914, 

 p. 69; E. informis, Stephens, 1915, p. 450, pl. xi, fig. 11; E. fucorum, Stephens, 1921, p. 17; 

 E. normani, Brondsted, 1923, p. 138, fig. 18; E. crasso-fibrosa, id., he. cit., p. 139, fig. 19; 

 E. edzvardii, Dendy, 1924, p. 341; E. normani, Brondsted, 1926, p. 5; Amphihetus gracilis. 

 Burton, 1929, p. 428; Axinosia incrustans. Burton, 1930, p. 333, fig. i. 



Occurrence. St. 6: Tristan da Cunha, 80-140 m.; St. 42: South Georgia, 120-204 m.; St. 51: 

 Falkland Islands, 105-11501.; St. 160: Shag Rocks, 177 m.; St. WS 83 : Falkland Islands, 137- 

 129 m.; St. WS 229: Falkland Islands, 210-271 m. 



Diagnosis. Sponge polymorphic, encrusting, massive, or branching ; surface even, 

 minutely hispid ; oscules inconspicuous in encrusting forms, small and scattered or large 

 and crateriform in massive forms, small, often arranged in linear series in branching 

 forms; skeleton isodictyal to sub-isodictyal ; no special dermal skeleton; megascleres 

 smooth, usually curved styli, o-i35-o-48 by o-oo3-o-oi9 mm. ; microscleres palmate 

 isochelae, o-oi4-o-028 mm. 



Remarks. Bowerbank, in his Monograph of the British Spmigiadae (1866-82), de- 

 scribed twelve species of Isodictya possessing styli and palmate anisochelae. All agree so 

 very closely in spiculation that, judging from this aspect alone, there would be no 

 hesitation in regarding them all as synonyms of a single species. Certain differences in 

 their external appearance give rise, however, to a little hesitation in taking so drastic a 

 step, and it is necessary to compare them from this point of view. 



/. normani is massive with large, crater-like oscules, or encrusting with small, scattered 

 oscules ; colour (alive) unknown, (dried) fawn-yellow. 



/. fucorum is massive with comparatively large, scattered oscules; colour (alive) 

 "bright red or pink, to pale ash or brown". 



I. alderi is encrusting, with inconspicuous oscules ; colour (alive) faint red. 



/. edzvardii is encrusting, with inconspicuous oscules; colour (dried) "ochreous 

 yellow". 



