Dr. W. Djbowski 07i Lubomirskia baicalensis. 29 



gtructure (? product of fossilization) ; d, hourglass-shaped 

 canal tilled with grains of quartz-sand; e e e, piu-Uke spicules 

 in the " calcite," arranged arouud the funnel-shaped openings 

 of the hourglass-canals outside respectively, as will be better 

 understood by the next tigure, but here only seen in the section, 

 where they may be ob.^erved to slope inwards with the head ex- 

 ternally ; ff, row of triradiate spicules in the " calcite " within 

 the pin-like spicules. Diagrammatic, with the detail relatively 

 magnified. 



Fig. 9. The same. Pin-like spicule, more magnified, to show its shape 

 and relative proportions. 



Fiff. ^^- The same. Vertical section of a portion of the wall at the infla- 

 tion, viewed from the inside, magnified to the same scale (see a 

 less magnified portion, fig, 7). a a, wall composed of the homo- 

 geneous crystalline calcite with minute fibrous structure before 

 mentioned ; hhh, constricted parts of the hourglass-shaped 

 canals, respectively filled with quartz-sand, also as before men- 

 tioned \ c cc, position of the triradiate spicules in the wall 

 around the hourglass-canals, shown by their truncate ends ; d, 

 part of the slice where the layer of triradiates has been 

 ground off, showing that ee e, the cross-sections of the pin-like 

 spicules, are in circles, indicative of their infundibular mode 

 of arrangement around the external openings of the hour- 

 glass-shaped canals. Diagrammatic, with the detail relatively 

 magnified. 



III. — Some EemarJcs upon the Variability of Form in Lubo- 

 mirskia baicalensisj and ui^on the Distribution of the Baikal 

 Sponges in general. By Dr. W. Dybowski *. With P.tSS. 

 by H. J. Caktee, F.K.iS. &c. 



[Plate II.J 



During the printing of mj memoir on tlie sponges of Lake 

 Baikal t, I received from Irkutsk, from my brother Dr. Bene- 

 dict Dybowski, a photographic representation, prepared by 

 him, of Lubomirskia baicalensis^ and also a communication 

 upon the general occurrence and distribution of sponges in 

 Lake Baikal. These notes possess no little scientific interest, 

 and may therefore serve to complete my memoir, so that I 

 regard it as advisable to publish them as a brief supplement 

 to my work above cited. 



* Translated from a separate copy, communicated by Mr. Caiter, of the 

 paper published in the ' Bulletin de I'Academie des Sciences de St. 

 Petersbourg,' tome xxvii. pp. 45-50. 



t W. Dybowski, " Studien liber die Spongien des russischen Peiches 

 ]nit besonderer Beriicksichtigung der Spongien-P'auna des Baikal-Sees," 

 in Mem. de I'Acad. des feci, de St. Petersb. ser. 7, tome xxvii. no. 6 

 (1880). 



