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



Marshall/ cannot be separated even specifically from Spongelia pcdlescem, Nardo. Not- 

 withstanding, in England, the name Dysidea has not been given up, and in order to 

 reconcile English and Continental naturalists, Marshall proposed to retain both these 

 names in order to apply them to different forms. He groups Johnston's Dysidea 

 fixigilis in the genus Spongelia as restricted by F. E. Schulze, and, on the other hand, 

 Bowerbank's species Spongelia coriacea and Hyatt's Spongelia fragilis in the genus 

 Dysidea, giving it a new and detailed diagnosis, and in harmony with Hyatt — who 

 four years before also retained both these genera, and even grouped them in different 

 families on the ground of a thoroughly false supposition as to the manner of grou-th of 

 the horny skeletal fibres — and, I repeat, in harmony with Hyatt, demands a more 

 pronounced separation of both these genera. This latter view is expressed in a report on 

 his own memoir on Dysideidse and Phoriospougise,^ while in the memoir itself (foe. cit., 

 p. 91) he seems to be of a rather different opinion, writing as follows : "Ganz scharf zu 

 trennen siud diese genera freilich nicht, so wenig wie Euspongia und Cacospongia, diese 

 und Spongelia." This is, however, of little consecpience indeed, but unfortunately, on 

 the whole, instead of having simplified the matter Dr. Marshall complicated it still more. 

 The series of his Dysideidse in the paper above mentioned he opens by the newly created 

 genus Psammascus, characterising it by a great number of peculiarities, each of which, 

 however, must be regarded as almost devoid of any systematic importance. This is also 

 but of little consequence ; it is not for the first time that in the Keratosa bad genera 

 have been established and bad generic definitions given, but Dr. Marshall adds to the 

 above definition the following remark : " Of all Dysideidaj this genus (Psam^nasciis) 

 shows the closest affinities to the genus Spongelia, being however to be readily 

 distinguished from it by the presence of foreign enclosures also in the soft parts. "'^ If 

 now the reader will compare the definition Dr. Marshall gives of his genus Psammascus 

 {loc. cit, p. 92) with that by which he describes the genus Dysidea [loc. cit., p. 98), he 

 will find that this latter genus — apart from the character consisting in the presence of 

 a skin containing numerous foreign enclosures and to be easily di'awn off (a character of 

 a very doubtful systematic consequence,* but for which nevertheless Dr. Marshall evinces 

 the greatest predilection)— differs from Psammascus only in the presence of foreign 

 bodies in the parenchyma ; and, when I add, in harmony with F. E. Schulze,^ that 

 Dr. Marshall has been quite wTong in supposing the true representatives of the genus 

 Spongelia, in the sense of F. E. Schulze, to be devoid of any foreign enclosures 

 both in the parenchyma and in the dermal membrane ; when I further mention that 

 neither in Dr. Marshall's paper on Dysideida) nor in the highly detailed and precise 

 memoir on the genus Spongelia by F. E. Schulze are any statements to be 



1 Zeitschr. f. wiss. Zool., Bd. xxxv. p. 91. 2 Jahresb. d. zool. Stat. Neapel, 1880, p. 178. 



2 Zeitschr. f. iviss. Zool., Bd. xxxv. p. 92. 



* Coiiip. F. E. Schulze's discussion of the question in Zeitschr./. vdss. Zool., Bd. xxxiii. p. 14. 

 ^ Zeitschr./. wiss. Zool., Bd. xxxii. ^t. 1.36. 



