Sponges jrom the Atlantic Ocean,* 311 



The jar inwhich this is contained bears on its label "25, 75-374 

 fathoms, a few miles north of Cape St. Vincent." Here 

 75-374 maj mean " from 75 to 374 " fathoms. Besides 

 the sponges mentioned, the jar contains Corallistes Boicer- 

 hankii, Azorica Pfeifferce^ Pachastrella abyssi^ Stelletta pachas- 

 trelloides, n. sp., Phakellia ventilahrum^ &c. The portion of 

 Isodictya is laminiform, about half an inch in diameter, and 

 l-24th inch thick. Its surface is even and covered with holes 

 (? pores and vents respectively), while the interior consists of 

 an areolar structure easily crushable, and composed of sarcode 

 charged with one kind of spicule only, which is arranged in 

 bundles end to end, and crossing each other in accordance 

 with the kind and form of the areolar structure common to 

 the Isodictyosa. The spicule is straight, cylindrical, bent 

 abruptly close to each end and rounded terminally ; but while 

 one end is turned in one direction, the other is not turned in 

 the opposite, but laterally, so that when the bend of one end 

 is seen the other is obscured by being in a line with the 

 shaft ; besides this, the shaft is sparsely covered throughout 

 with short erect spines, except at the ends which are smooth, 

 about 50- by 2-6000ths inch (PI. XV. fig. 42). Size of entire 

 specimen half an inch in horizontal diameter. 



Hah. Marine, on hard objects. 



Loc. Above mentioned. 



Ohs. The most remarkable point about this little specimen 

 is the peculiar character of its spiculura. 



Thalysias, Duchass. de Fonb. et Michelotti. 



There are three small specimens of Thalysias^ two of which 

 are on large fragments of Corallistes Bowerhankii from sta- 

 tion 25 = 374 fathoms near Cape St. Vincent, and the other 

 separate in a jar numbered 6=345 fathoms N.W. of the 

 Shetland Islands. All present the chalky-white appearance 

 characteristic of the sponge to which Duchassaing de Fon- 

 bressin et G. Michelotti have given the name " Thalysias " 

 (' Spongiaires de la Mer Caraibe,' pi. xvii. fig. 1), and consist 

 of two or three papillae, open respectively at the summit ; but 

 when examined microscopically two are found to present only 

 one kind of spicule, which is nearly cylindrical, curved, smooth, 

 and round at the ends, 28- by l|-6000th inch; and the other 

 two kinds of spicules, viz. a skeleton- and a flesh- spicule; 

 of which the skeleton-spicule also is nearly cylindrical, curved 

 and smooth, but abruptly pointed at the ends, 45- by 2|-6000ths 

 inch, and the flesh-spicule a fine tricurvate, 9-6000ths inch long. 

 This is the first time that I have found the skeleton-spicule of 



21* 



