22 THE VOYAGE OF H.M.S. CHALLENGER. 



Spicules. — Small, slender oxea, very slightly curved ; abruptly and often bluntly 

 pointed; size about O"! by 0-0032 mm. 



This species diflfers from Pachychallna {Cladochalina) diffusa, Ridley,^ in the 

 inferior amount of spongin in the fibre, in the slenderer spicules (0-0032 as against 

 0-0063 mm. thick) and in the much larger oscula. 



Localities. — " Off Bahia, 7-20 fathoms"; several pieces. " Off Bahia" (inside label); 

 •■' off Bermuda, shallow water " (outside label) ; several pieces. 



Station 208, January 17, 1875; lat. 11° 37' K, long. 12.3° 31' E.; Philippine 

 Islands; depth, 18 fathoms; bottom, blue mud. One small specimen (PL IV. fig. 4) 

 of a vai-iety, differing slightly in external appearance, but agreeing closely in micro- 

 scopical structure, size of spicules, &c. 



Pachychalina lobata, Ridley (PL V. fig. 1 ; PL XLVI. fig. 4). 



1884. Pachychalina lohata, Ridley, Zool. Coll. H.M.S. "Alert," Brit. Mus., p. 404. 



The ChaUenger obtained one specimen of this sponge (PL V. fig. 1), which, being in 

 much better condition than the single specimen obtained by the " Alert," and described 

 by Ridley {he. cit.), enables us to add some interesting details. The specimen in question 

 consists of a single, long, compressed, digitate process ; it has apparently grown erect 

 and measures 200 mm. in length, 16 mm. in breadth, and a little over 8 mm. in thick- 

 ness. There is an almost uniserial row of circular oscula down each margin {vide 

 fig. 1), each osculum being about 2 mm. in diameter. The dermal membrane is delicate 

 and transparent, supported l3y a very beautiful and regular reticulation of spiculo-fibre. 

 The pores are very numerous, reducing the dermal membrane in the meshes of the 

 dermal reticulation to a mere network (PL XLVI. fig. 4). 



This specimen differs from the type of the species ; (1) in the size of the spicules, 

 which measure only about 0-16 by O'OllS mm. as against 0-21 by 0-0128 mm.; (2) in the 

 possession of a more highly developed and regular dermal skeleton reticulation. That there 

 is a similar dermal reticulation in the original type we have convinced ourselves by a 

 re-examination of the specimen, but it is not so well developed as in the Challenger sponge ; 

 and thus the original description is incorrect in so far as it is stated that the dermal 

 skeleton is " a closely-set coat of subparallel spiculo-fibres." 



The specific name lohata was given by Ridley on the supposition that the species was 

 identical with Esper's Sjwngia lohata,^ but we have now arrived at the conclusion that 

 this identification is untenable; hence the "Alert" specimen must stand as the type 

 of Pachychalina lohata. 



Locality. — Port Jackson ; 30 to 35 fathoms. One specimen. 



Ilahltat.—? oxt Darwin, Australia (Ridley, "Alert"); Port Jackson, Australia 

 (Challenger). 



' Ann. ;ui(1 Mag. Nat. Hist., ser. 5, vol. xiv. p. 183. ^Hie. Pflanzenthiere, vol. ii. p. 273, pi. xlvi. 



