410 On Deep-sea Sponges from the Atlantic Ocean. 



throughout its course a number of short blunt spines of dif- 

 ferent lengths, chiefly radiating from the ends, and more or less 

 congregated at two points on the body of the shaft (fig. 41 a), 

 5-6000ths inch long ; 2, minute, also bacillary in the shaft, 

 which is moreor less twisted, and presents a numberof fine, thin, 

 long, linear spines, chiefly congregated about the ends, so as to 

 assume a bistellate appearance, 2^-6000ths inch long (fig. 41, Z;). 



Pachastrella parasitica^ n. sp. (PI. XVI. fig. 50 &c.) 



Like the foregoing, but not belonging to the sponges 

 dredged up on board the ' Porcupine,' is a Pachastrella which 

 I have lately found on a specimen of Polytrema utriculare 

 ('Annals,' 1876, vol. xvii. p. 211, pi. xiii. flg. 17, a, b), and 

 have therefore designated ^^ parasitica.^ ^ Locality unknown. 

 The linear, acerate (PI. XVI. fig. 50, c), and ramular skeleton- 

 (fig. 50, a), with the bacillary spinous (fig. 50, d) and minute 

 stellate (fig. 50, f) flesh-spicules are, mutatis mutandis, the 

 same. Here, however, the branches of the ramular skeleton- 

 spicule are thrice divided, not " twice " only, as erroneously 

 figured and stated in the 'Annals ' (Z. c), where also the shaft 

 should have been prolonged anteriorly. The large bacillary 

 spined flesh-spicule, too, is thin, slightly undulating and thickly 

 beset with minute spines like that of Pachastrella abyssi; but 

 we have not the distinguishing character of the latter here, 

 viz. the thick, solid, sZ:;^V</e-shaped flesh-spicule. 



Had not my attention, at the time I alluded to this species 

 in the 'Annals,' been chiefly taken up in examining the orga- 

 nism on which it is parasitic, I should not have made the 

 mistakes in delineation &c. to which I have above referred ; 

 while now that it is specially called to the sponges, I have the 

 opportunity of correcting them. 



All the species oi Pachastrella, beginning with Dercitus niger 

 of our coasts, are amorphous, and are in the habit of pene- 

 trating any crevices over which they may be growing; so that 

 they are often found in the midst of the branches of old corals 

 and deciduous shells, in company with a boring Cliona, which 

 they follow but do not precede. Again, they do not reject 

 hard objects with which they may come into contact during 

 growth, especially P. abyssi, which appears to incorporate 

 every thing of the kind it meets with, in which these sponges 

 very much resemble fungi. 



With the shaft being often prolonged beyond the giving-off 

 of the branches in P. parasitica, together with the twisted 

 and divided form of the distal bifurcations, we have a ramular 

 form which seems to lead into the still more complicate one of 

 the Lithistina. 



[To be cuntinuedj. 



