., PORIFERA. III. 



Leptolabis; below I have separated off the species with ancorse, forming for them my genus Hymen- 

 ancora; though it is only a small number of species which are thus separated from Hymedcsmia, the 

 division is, however, of importance, making the remaining genus more uniform and natural. The 

 possibility might also be suggested of dividing the remaining genus into two, containing respectively 

 the species with and those without rnicroscleres, but such a division I consider as not natural, as 

 some species of both groups are nearly related; quite the same holds good with regard to the pos- 

 sibility of separating off the species which possess sigmates, e. g. H. zetlandica Bow. with sigmates is 

 nearly related to II. Bowerbanki n. sp., truncata n. sp. and latrunculioides n. sp. all without sigmates. 



i. H. Koehleri Tops. 

 PI. V, Fig. 5. 

 1896. Leptosia Koehleri Topsent, Resultats scient. de la camp, du "Caudan", 284, PL VIII, fig. 7—9. 

 1904. Topsent, Resultats des camp, scient. du Prince de Monaco, Fasc. XXV, 188. 



Incrusting ; oscula present as low and indistinct cones, with a dense skeleton of dermal spicules 

 in the wall. Spicula: megasclera; the skeletal spicules acanthostyti with a somcwliat distinct head, and 

 spined in the whole or nearly the whole length, o-og — o-jj'"'", not divided into two groups; dermal spi- 

 cules polytylote strongyla o-iq6 — o'jo"""; microsclcra chela> arcuattc 0-028 — o-ojo' 



.mm 



Of this species, whicli I refer to it. Koehleri Tops, (see below under remarks), we have a rather 

 large material. The specimens form thin incrustations on stones, some single ones grow on tubes of 

 Placostcgus tridental us The greatest extent to which my specimens reach is 24 mm ; the thickness 

 reaches scarcely 0-5 mni . The colour (in spirit) is generally white, sometimes a little darker and then 

 greyish brown or light brown. The surface is in the undamaged specimens smooth, without projecting 

 spicules, but under a good lens it appears finely gritty, which is caused by the styles. The dermal 

 membrane is an easily separable, thin and transparent membrane; it is filled with rnicroscleres and is 

 supported by scattered bundles of dermal spicules. Pores I have only observed with certainty in a 

 couple of specimens, and in these they were seen as scattered, circular openings of a diameter of about 

 0047 n,m ; when the pores are normally open they probably lie in groups over the subdermal cavities. 

 Oscula could in several specimens be observed with a good lens. They are scattered on the surface 

 and appear as very weakly pronounced and low cones of a diameter of about i mm . In the centre an 

 opening appears which is larger or smaller in relation to the degree of opening of the osculum; on 

 account of the slight thickness of the sponge the opening only appears as a deepening; when the 

 osculum is closed, the cone appears slightly stellately corrugated. The dermal spicules form an oscular 

 skeleton, as they lie very close in the wall of the oscular cone and are arranged subparallel, so that 

 they radiate stellately towards the oscular opening; above the dermal spicules, however, lies the dense 

 layer of chelae; this layer is only wanting just at the very summit of the oscular cone. Larger and 

 smaller subdermal cavities or canals may be seen shining through the dermis, especially in the lighter 

 coloured specimens. 



The skeleton. The dermal skeleton may be said for the greater part to be formed of the chelse, 

 which form a very dense layer in the dermal membrane. Moreover, short and loose fibres or bundles 



