176 



PORIFERA. II. 



1885. Alebiou piceum Vosmaer, Bijdr. tot de Dierk. i2te Afl., 3die Gedeelt. 31, PI. V, fig. 50. 

 1887. Esperia nigricans Fristedt (non Bow.), Vega Exp. vetensk. Iakttag. IV, 448. 



Erect, leaf-shaped, or more irregular, lobate with smaller or larger lobes. One surface generally 

 zvith more or less shallow grooves, separated by ridges. The surface smooth. The dermal membrane a 

 distinct, but thin film, zvith a skeleton of horizojital dermal spicules forming on the pore side a reticu- 

 lation, and being scattered on the oscular side; it is supported by pcnicillatc bundles of dermal spicules. 

 Oscula numerous, scattered on the even surface, pores in grooves on the opposite surface. The skeleton 

 a rather close, irregular, polyspicular retiadation. Spicula: Megasclera : the skeletal spicules more 

 or less spined acanthostyli 0-26 — 0-4 f""', the dermal spicules tylota zvith spined ends 0-238— 0-298"""; 

 microsclera of two forms, anisochela> palmata: of the Iophou type 0-016 — 0-036"'"', bipocilla 0-008—0-014 



mm 



This species may have a somewhat varying appearance, but typical and well developed speci- 

 mens have a quite characteristic form. The species is always erect and more or less leaf-shaped, but 

 sometimes somewhat irregularly folded or curved, so that various, but then always irregular, some- 

 times somewhat cup-shaped forms arise, or the form becomes still more irregular, more or less lobate. 

 It is attached with the base to the sea-bottom, or to things on the bottom, and the most regular 

 specimens form a rather thick, oval leaf, which is broadest below, not being restricted here. What 

 gives to the species its characteristic appearance, however, is its two surfaces. They differ from each 

 other first in the fact that one is the oscular side, the other the pore side, but other differences are 

 also found. The oscular surface is most frequently tolerably smooth, or shows only a few irregular 

 and oftenest shallow grooves. The pore surface, on the other hand, has a number of more or less 

 deep grooves of varying sizes, separated by walls of varying breadths. The grooves are of an irregular 

 form, and the walls between them may be undulating or sinuous. These grooves are distinctly present 

 in far the greater number of specimens and give to these a characteristic appearance. They may, 

 however, be conspicuous in different degrees, especially they may be fewer, and then they are larger 

 and more shallow , and consequently less characteristic. The described form of the sponge is the 

 one most frequent and characteristic; but it may also by transitions pass into a thinner leaf-shaped 

 form, especially as to the upper part of the sponge. It is especially in such forms that the grooves 

 of the pore side become large and shallow, and they ma) - quite disappear, so that the leaf-shaped 

 sponge shows more or less even surfaces. Thus the extremities with regard to form seem on one 

 side to be the quite irregular, more or less lobed forms, on the other side the quite leaf-shaped 

 ones, and the middle form between these extremities is found in the regular, grooved specimens 

 of the first described form, which seems to be the most frequent and most normal form of the 

 sponge. Unfortunately, only few tolerably entire specimens are found in the material in hand, but a 

 great many fragments; therefore I am not able to speak of the variation in form with absolute cer- 

 tainty. The largest typical specimen is ca. i65 mm high, ca. i25 ram broad, and ca. 35"™ thick. The smallest 

 specimen among the tolerably entire ones has a height of 35""", a similar breadth, and is rather thin. 

 The largest quite leaf-shaped specimen has a height of ca. 140"™, a breadth of 2i5 mm , and a thickness 

 in the middle of ca. io mm ; thus it is considerably thinner than the typical specimens. The consistency 

 is brittle and little elastic, and the specimens are therefore easily broken; the thin, leaf-shaped speci- 



