r. PORIFERA. I. 



Grimm, and flava Grimm, have only been found in the Caspian Sea (Dybowski: Studien iiber Spong. 

 des russ. Reiches, Mem. de I'Acad. imp. des Sciences de St. Petersb. Ser. 7, Tom. 27, Nr. 6); the fourth, 

 M. Filholi Topsent (Resultats des camp, scient. du Prince de Monaco, Fasc. II, 70, PI. IV, Fig. 7, PI. IX 

 Fig. 6) is from the Azores. 



Petrosia \^osmaer. 

 (Schmidtia Balsamo CrivelH.) 



Tit e form varying. The consistency very Iiard. altiwst stony. Generally several, soinetivies -nu- 

 merous, circular, sharply defined oscula. The skeleton consisting of a close reticulation of thick fibres or 

 more or less diffuse. Spongin (soiiietintes) present to a small degree. Spicula oxea or strongyla, most 

 frequently short and thick. 



P. crassa Cart. 

 PI. IV, Figs. 7—9. PL XII, Fig. 5 a, b, c. 

 1876. Rcniera crassa Carter, Descript. and Figures of Deep-Sea Sponges etc. on board Porcupine ■, 

 Ann. Mag. of Nat. Hist. Ser. IV, Vol. XVIII, 132. 



The form more or less irregularly roundish, tuberous or lobate. The skin ivith a dense reticulation 

 of spiculofibres. Oscula scattered, circular with a sharp edge. The skeleton consists of a more or less 

 regular network of polyspicular fibres, and besides some scattered spicules. Spongin present to a small 

 degree. Spicula oxea, dividing into tifo rather well separated groups of size ; the length of the larger 

 o'2 — crjj""". of the smaller ca. o-o8 — o'lj""". Further quite short oxea, sfroitgyla. and other forms are found. 



This sponge is of an irregularly tuberous or lobate form. Most frequently it is attached to a 

 small stone, from which it spreads, sometimes more in height, sometimes more to the sides, assuming 

 a tuberous or lobate form. The smaller specimens are more roundish, the larger more irregularly lo- 

 bate. The largest specimens reach a greatest extent of 13'"°. The consistency, as in the genus Petrosia 

 upon the whole, is hard, almost stony, the tissue, however, being brittle. The colour (in spirit) is 

 whitish or more or less yellowish. The surface is smooth. The ski)i scales off easily, and is provided 

 with a close reticulation of spicules, in some places closer than in others. Oscula are, in the specimens 

 in hand, found to a number of from two to five. They are very much varying in size, of a diameter 

 of 2 — II"""; they are always almost circular, and the skin surrounds them with a sharp edge. Other- 

 wise their structure is very characteristic. The\' ma\' be deeper or more flattened, and the excurrent 

 canals open into them very close to each other, the openings being rather regularh- arranged in a ring- 

 like manner. The arrangement of the system of canals is connected with this feature, as the canals appear 

 to be arranged into two systems, as mentioned by Vosmaer (Porifera 132, Tab. VI, Fig. 9). To be sure, 

 in specimens cut through, the arrangement is not seen so distinctly prominent as in the figure of Vos- 

 maer; but this may probably be owing to the fact that the arrangement is somewhat modified b>- 

 the irregular form of the present species. It may, however, be seen rather distinctly (PI. I\', fig. 9) that 

 the excurrent canals meet in the osciilum in a radiate way; a system of canals at right angles to the 

 latter, is, on the contrary, only indistinctly seen. Immediately below the skin a great man)- canals are 



