REPORT ON THE MONAXONIDA. 109 



here for the first time describes and figures the peculiar chelate spicule, but makes uo 

 mention of such spicules in Johnston's sponge, nor does Johnston himself mention them 

 in his original description [loc. cit.). Fortunately, ]\'Ir. H. J. Carter ^ has found these 

 spicules in Johnston's type in the British Museum, and thus the identification of 

 Bowerbank's with Johnston's species is confirmed ; though Mr. Carter places them both in 

 the genus Chalina. Dr. Gray in his remarkable paper in the Proceedings of the Zoological 

 Society of London (May 1867), appears to recognise the fact (which is undoubtedly 

 true) that Dr. Bowerbank's genus Isodictya is much too comprehensive ; he therefore 

 very wisely splits the genus up into several genera, but unfortunately in so doing he 

 retains the name Isodictya for two of these distinct genera, giving to each a distinct 

 generic diagnosis. With his first genus Isodictya (loc. cit., p. 512) we have here 

 nothing to do. Of his second (p. 534) he gives the following diagnosis. " Sponge 

 sessile, minutely hispid, regularly reticulated. Spicules of three kinds : — 1. Needle- 

 shaped, fusiform. 2. Bihamate, bicalcarate (Bowerb., f. 121). 3. Equianchoratc 

 or palmate." Of this genus he gives Isodictya normani, Bowerbauk, as the type, 

 and says, " see also ..../. palmata, Bowerb." Unfortunately Isodictya palmata, 

 Bowerbank, has only two kind of spicules. 



Dr. Ehlers (Die Esper'schen Spongien, p. 16) identifies Esper's old species, Spongia 

 digitata,'^ with Johnston's Halichondria 2Jabnata and Bowerbank's Isodictya p)cdmata. 

 He recognises (pp. 35, 36) that both Gray's genera Isodictya cannot stand, and creates 

 for Esper's species, digitata, the new genus, Homceodictya, without, however, giving a 

 fresh generic diagnosis, and apparently intending the new genus to replace Gray's second 

 Isodictya. 



Here, then, arises a considerable uncertainty as to the correct nomenclature, not only 

 of the genus, but also of the species known as palmata. 



For the present we retain the name Homceodictya for the subgenus, and include 

 therein only three species, viz., Desmacidon (Homceodictya) palmata, Johnst. (1 = Spongia 

 digitata, Esper), and the two new species Desmacidon (Homceodictya) kerguelen- 

 ensis, nobis, and Desmacidon (Homceodictya) grandis, nobis, all characterised by the 

 peculiar form of the isochelate microsclera. 



The above does not pretend to be a complete history of the subgenus, which time 

 and space do not permit, and it will be seen by reference to Johnston (loc. cit.) that 

 there is still a considerable amount of literature to which we have not alluded. It 

 appears to us that the characters separating the three species of Homceodictya from 

 Desmacidon are only of subgeneric value, one very strong piece of evidence in favour 

 of this view being the intermediate position of Desmacidon conidosa, nobis. 



The peculiar backward process of the anterior palm of the chelate spicule is a 



1 Ann. and May. Nat. Hist., ser. 5, vol. x. p. 110. 



2 Esper, Die PflanzentHere, Fortsetzimgen, i. p. 190, pi. 1. 



