PORIFERA. I. 35 



polyspiciUar, as the skeleton upon the whole may be more irregular. The ends of the spicules are zinited 

 by more or less spongin. Spicula are short oxea or more rarely strongyla. 



The typical /Lf«/>ra-skeleton, consisting of quadratic or rectangnlar meshes formed by nnispi- 

 cular fibres, is very characteristic, but in many species the skeleton is more irregular; when this ir- 

 regularity is more pronounced, the skeletal structure approaches that of some species of Halichondria, 

 especially as the amount of spongin may be quite minimal; as a distinguishing character are then 

 only left the short, less slender spicules, but they will also generally be a good criterion with regard 

 to the referring of the species to the genus; the fact is that the Reniera-&^\cv\&s are characteristic by 

 being comparatively short and never so long tapering, as is most frequently the case in the Halicondria- 

 species. Also another feature is of importance as a distinguishing character. ]Most i?i';//rra-species 

 have a dermal membrane without spicules, resting on the underlying skeleton and pierced by the ends 

 of the primary fibres, while the Halichondria-ST^ecies have most frequently a dermal membrane with 

 spicules, through which no ends of fibres project; but also here transitions are found, as for instance 

 in the above mentioned species Halichondria oblonga and tenuiderma^ which with regard to this fea- 

 ture approach the Reniera. Fristedt (Vega Exp. vetensk. lakttag. IV, 425) calls attention to a similar 

 fact, and mentions Halichondria (Amorphina) renieroides as also approaching the Reniera in this 

 respect. In this species, however, it is not the ends of fibres that project, but a dense spiculation is 

 found of spicules a little projecting and perpendicular on the surface; therefore with regard to this 

 feature the species is not especially nearly allied to the Reniera. From the reasons given above, 

 species with a less regular skeleton, and with exceedingly little spongin, but with short, never espe- 

 cially long and evenly tapering oxea, have in the present work been referred to Reniera. 



On the other hand Reniera-s^&c\&s, as has been mentioned under the Chalinines, may by a 

 development of spongin approach these latter in skeletal structure, so that no sharp limit can be drawn. 



I. R. urceolus Rathke et Vahl. 

 PI. I, Fig. 6. PL XI, Fig. I. 

 1806. Spongia urceolus Rathke et Vahl, O. F. Miiller Zoologia danica IV, 42, Tab. CLVII, fig. 3. 

 1870. fChalinula robustior O. Schmidt, Grundziige einer Spongienf. des atlant. Gebiet. 38. 



Oblong-pyriform, stalked, sometimes branched or showing several coalesced tubes. The dermal 

 membrane thin, -without spicules; the ends 0/ the fibres projecting and the surface accordingly finely 

 shaggy. In the upper end a large osculum leading into a wide oscular canal riinning throughout the length. 

 The skeleton a rather regular network of primary and secondary fibres with quadratic meshes; the fibres 

 unispicular. Particular polyspicular fibres are found running from the stalk longitudinally through the 

 sponge. Spicula comparatively thick, slightly ctirved oxea, ca. 0-208""". 



This sponge of which we have two whole specimens and some more or less damaged fragments, 

 is in its most regular shape oblong-pyriform, and is below produced into a short stalk, by which one 

 specimen is attached to a little stone, while the other is torn off. The larger and more lengthened 

 specimen has a length of lo^™, and a greatest breath in the middle of 3'^"'. The other specimen is 

 smaller and comparatively less lengthened; it has a length of 7"^'", and a greatest breath of 2-4'^"^. One 



5* 



