PORIFERA. II. 117 



transiens and rimosa smooth ones, and in apollinis both kinds seem to be found. Therefore it is 

 perhaps doubtful whether the genus in future will prove to be a natural one; but at present it 

 must be maintained. If it were to be dissolved, the species, on account of their spiculation, might 

 best be referred to Esperiopsis, in which genus we have already species with the same combination 

 of microscleres, but not, however, with spined bows. - - What is also to be noticed is the great resem- 

 blance with regard to spiculation which most species of the genus show with Hymeraphia and Rha- 

 phidophlus, of which genera styli, dermal styli with slightly spined head-end, isochelae palmatae of 

 nuite the same form as in Artemisina, and toxa are characteristic. 



Homoeodictya Ehlers (emend.). 



The form very varying, from thick incrustations through more massive sponges to erect ones of 

 various forms, sometimes plate-shaped, or digitately branched of a Chalina-like appearance. The skeleton 

 also very variously developed, diffuse, irregularly polyspicular, or forming a regular reticulation with pri- 

 mary fibres bending towards the surface in a fan-shaped way, and secondary fibres. Spongin present in 

 varying degree, sometimes, in the most Chalina-like species, in rather great amount, forming sheaths 

 round the fibres. Spicula: J/egasclera diactiual, oxea or strougyla ; microsclera isochehe palmata 1 or 

 arcuatir, to which may be added rhaphides (and perhaps sigmata). 



Ehlers, who recognized that Bowerbank's genus Isodictya, in which the species palmata 

 was found, was too heterogeneous, established for palmata the genus Honuvodictya (Die Esperschen 



Spong. Program zum Eintritt in dem Senat , Erlangen 1870, 17 et 32), attaching special importance 



to the equi-ended chelae 1 ). On the other hand he laid no stress on the special form of the chela, 

 which he described, however, in the specific description. Ridley and Dendy, in Challeug. Report, 

 regard Ilomasodictya as a subgenus of Desmacidon, but they use as a diagnostic character the peculiar 

 bending in of the axis in the chela, and they refer to the subgenus only three species all of which 

 show this character. As mentioned in the introduction, such genera containing species with ancorae 

 and species with chelae must be divided, and this is exactly the case with the genus Desmacidon. 

 The species of this genus must be divided in two groups, one with aucorae, the other with chelae. 

 As the type of the genus Desmacidon, D.fruticosus Bow. has ancorae, the generic name of Desmacidon 

 must be kept for the species with ancorae. The question might then be of forming a new genus for 

 the other group. I think, however, that it will be more correct, at all events at present, not to under- 

 stand Hoviosodictya in the restricted sense in which it was understood by Ridley and Dendy, but 

 to enlarge it to comprise all species of the old genus Desmacidon with chelae. I think that these 

 species are naturally connected; to be sure there is, as shown by the diagnosis, some difference as to 

 form and skeletal structure, but the species seem here, as in several other genera, to form a continuous 

 series; H. conulosa R. and D. occupies, as already stated by the authors, an intermediate position. As 

 to the microsclera, the genus will comprise forms with arcuate chelae, with common palmate chelae, 



') Ridley and Dendy say that Ehlers established the genus without giving any diagnosis; this, however, is not 

 the case, as Ehlers, on p. 32, gives a diagnosis of the genus rather good for its time. 



