sroxGiiDA. 453 



strongly recurvate ; 6ize of spicule "07 by -0095 millim. : very 

 abundant on the fibre. (4) Navicular e<iuianchorate of sarcode, 

 shaft slender, almost straight; length of spicule *018 millim. 

 Hdb. Prince of Wales Channel, Torres Straits, 5-7 fms. 



ACARNUS. 

 Gray, P. Z. S. 1867, p. 544. 



Acamia is used as a generic name in an earlier part (torn. 

 cit. p. 515) of the same paper as that in which Dr. Gray described 

 Acamus ; but it has not come into general use, otherwise the 

 essential agreement in form between the two words would neces- 

 sitate the suppression, on that ground, of the later one. A careful 

 comparison of the grapnel-spicule, which characterizes the genus, 

 with the spined cylindricals of Olaihria and Echinodictyum shows 

 that the affinity of the sponge is with these genera rather than with 

 the " Tethyadaj" of Dr. Gray, as held by him, or with the " Esperiadae," 

 as supposed by Mr. Carter (Ann. & Mag. Nat. Hist. 1871, vii. p. 274). 



A. innominatus, Gray* (I. c), besides the remarkable 4-hooked 

 grapnel-like spicule and the acuate (not cylindrical, as stated by 

 Gray, I.e.) form wbich characterize the main skeleton, possesses — as I 

 have been able to ascertain by an examination of a mounting made 

 by Dr. Bowerbank, who was the first to figure and describe these 

 spicules (Mon.Brit. Spong. i.figs. 73-76, 292), which Dr. Gray after- 

 wards embodied in his description of the species — also a tricurvate 

 (figured by Bowerbank) and an equianchorate flesh-spicule ; the 

 former about "13 by "0042 millim. in dimensions, the latter '016 to 

 •024 millim. long ; also a tibiella, measuring about "28 by '0045 

 (shaft) or -0063 (head) millim. 



82. Acarnus ternatus. (Plate XLII. figs. 6, 6'.) 



Prom a mounting which the Museum owes to the liberality of Dr. 

 John Millar, and from the spirit-specimen in the present collection, 

 we learn that in this new species the acuate spicules are imbedded 

 in a reticulate horny skeleton of a pale salmon-red colour, and not, 

 as usual, yellow. The grapnel has but three hooks, and the tibiella 

 has the shaft only '003 millim. thick. The other spicules agree with 

 those of A. innominatus. The largest of the present specimens is 

 about 65 by 25 millim. (2| inches by 1 inch), and forms a clathrous 

 structure of round soft anastomosing trabeculae which are about 

 3 millim. in diameter. Colour in spirit reddish brown. Several 

 specimens occur in the present collection. 



Hub. West Island and Prince of Wales Channel, Torres Straits, 

 7 fms. ; bottom sand and coral. 



Distribution. Bombay"? {coll- Brit. 2Ius.). 



* Mr. Carter gives reasons (I. c.) for his supposition that the West Indies 

 are the home of this species; the specimen, however, to which he appeals in 

 support of this view, viz. that attached to the base of a specimen of the West- 



