Sponges from the Atlantic Ocean. 473 



callisfes Bocagei\ also large fragments of CoralUstes Bower- 

 hankii^ Discodermia jwli/rliscu.'ij and Macandrewia azorica j 

 Piwliastrella abyssi, Slelletta jjachastrelloides^ and Geodia meya- 

 strelUiy the latter entire. 



Memoranda of other Organisms found among 

 THE Sponges. 



Polytrema miniaceum. 



On an old fragment of a brancli of dead coral about an inch 

 long and -^j inch thick, partly covered with Polyzoa, and 

 pierced witli holes of a Cliona, which was living in its inte- 

 rior, are five specimens of Polgtrema miniaceum with their 

 heads, as usual, broken off, leaving nothing but their lower 

 halves. This fragment was dredged up at station 24, =292 

 fathoms, a few miles north of Cape St. Vincent. With the 

 exception of these specimens, I have not met with even a 

 trace of Polytrema among the sponges dredged up on board 

 the * Porcupine ' north of this locality. 



Xanthidium abyssorum, n. sp. 



General form a spherical cell, covered with erect, conical, 

 transparent, hollow cim, ending in two or three short fila- 

 ments, straight and expanded, or recurved and curled. Cell 

 more or less filled with yellowish, granular, soft material. 

 Composition chitinous. Size of cell about 4-1800ths inch 

 in diameter; length of cirrus above l-1800th inch. 



Ilab. jMarine. 



Loc. Chops of English Channel, in 862 fathoms. 



Obs. This form of Xanthidium is found attached to Corti- 

 cium parasiticum where the latter covers the old stems of 

 Esperia cupressus, var. hamatifera. Nitric acid applied on 

 the slide causes the ends of tlie cirri to contract, but does 

 not dissolve the cell, which on drying and mounting loses its 

 sphericity, but not its diameter. The cirri, however, become 

 so transparent in the balsam that it is difficult to see them. I 

 possess a fossil specimen in flint, of precisely the same form, 

 only hardly half the diameter in the cell, wiiich is angulo- 

 spherieal by contraction, and tlie cirri a little longer. Pre- 

 cisely the same kind of cirri, too, are present in some winter- 

 eggs or statoblasts of the Bombay Lophopus which I have 

 mounted ; and the reasons may be seen ('Annals,' 18/59, vol. iii. 

 p. 342; , in my comparison of the winter-eggs of the freshwater 

 Bryozoa witii the seed-like body of Spotigilla, why I therein 

 stated that tlie results of my observations were " more in 



Ann. & May. N. Uist. Ser. 4. Vol. xviii. 32 



