1881.] THE fSTJRVEY OF H.M.S. 'ALERT.' 1 .S3 



increased by Carter (Ann. & Mag. Nat. Hist. ser. 4, xx. pp. 38, 40) 

 to include the Arctic region, is now extended southwards and into 

 the Pacific. 



Hab. Tom Bay (8. W. Chili), 0-30 fathoms ; on dead Retepora, 



Clathrina poterium, Hackel. 



Ascetta primorclialis, var. poterium, Hiickel, Kalkschwiimme, ii. 

 p. 17, pi. V. fig, \,f-i. 



Found in the form of a running tube {Auloplegma form), as in 

 («)ofthe preceding species; diameter of tube •2.5 to -.33 millim. ; 

 slightly pigmented with diffused red-brown pigment, concentrated 

 into a granular mass in some places (possibly due to a siliceous or a 

 horny sponge which grew in the neighbourhood). The triradiate 

 spicules are of two sizes, as shown by Hiickel for his iVustralian 

 variety poterium ; but they are connected by intermediate stages. 

 The large dermal form (which is occasionally bluntly pointed) varies 

 in the diameter of its rays from '019 to •02217 miilim. ; one ray is 

 usually about 7 : of tlie length of the other two, being from •13937 

 to •1774 m.illim. long, while the smaller rays are '1267 to •1584 in 

 length. The smaller, subdermal spicules have rays measuring about 

 •1J8 and '1207 (respectively, in the one spicule) by ^095 to 'OlOSG 

 miilim. The largest of the larger triradiates only form a single 

 surface layer ; the smaller subjacent forms are much more numerous. 

 The extreme diameter of the rays of the larger spicules is thus consi- 

 derably less than the average diameter given by Hackel for the Aus- 

 tralian form, viz. •025 miilim.; and the smaller spicule-rays are 

 considerably shorter in proportion to their length than in that form. 



Hab. Tom Bay (S.W. Chili), 0-30 fathoms ; on an Idmonea on 

 which a horny sponge was growing. 



Obs. I have followed Hackel's suggestion (p. 23, torn, cit.), and 

 advanced this form to the rank of a species, being justified, as I 

 consider, in this course by the fact that it is constant to its main 

 characters as described from the Australian specimens, even at the 

 great distance from which it is now recorded. It is distinguished 

 from d. primordialis, Hackel, by the minimum diameter of its largest 

 spicule-rays exceeding •02 miilim., and by the possession of a special 

 dermal set of triradiate spicules considerably krger than those 

 subjacent to them. 



Nardoa pelagica, sp. n. (Plate XI. fig. 4.) 



{Nardoa, Schmidt, Adr. Spong. p. 18; Ascandra, Hackel, Kalk- 

 schwamme, ii. p. 80.) 



Sponge forming a flattened cylinder, of about equal diameter 

 from the mouth to the base, which is almost flat. Length 19 mil- 

 lims. ; long and short diameters respectively 7 and 3 millims. Wall 

 1 miilim. thick. Lij) ? Skeleton consisting of scattered stout acerates 

 piercing the wall from the dermal to the cloacal surface, of an 

 external layer of triradiates whose longest ray either points inwards 

 or towards the base, of a less number of similar spicules inline- 



