South-Russian Spongillidse. 61 



The skeleton-spicules of the sponge under notice constitute, 

 as it were, a transitional form between the smooth and the 

 spiny Spongillid spicules*. The parenchyma-spicules are 

 also remarkably peculiar and characteristic. They are small 

 acerates, measuring 0*040-0'050 millim. in length and 0"02o- 

 0"010 millim. in thickness, and furnished with spines ; in form 

 they generally resemble those of Spongilla lacustris^ but the 

 form and arrangement of the spines are quite different from 

 those in the spicules of the latter Spongilla. Here the spines 

 occur in three different forms : the middle portion of the 

 spicule is beset with long, obtuse, vertically projecting spines, 

 but the two ends present small, pointed booklets, while towards 

 the middle of the spicule there exist pointed erect spines. 

 The long straight spines of the middle section are frequently 

 also covered with small acute spines ; the free end of the 

 spine is sometimes rounded off, sometimes truncated, and 

 sometimes furnished with a knob or a T-shaped rod. The 

 gemmules I have not been able to find, but I found in the 

 parenchyma of the sponges numerous amphidisci. 



The spindle-shaped amphidisci are very long ; their dimen- 

 sions are as follows : — 



millim. 



Total length 0-040-0-028 



Thickness of the shaft 0-002-0-004 



Diameter of the disk 0-012-0-010 



The shaft is furnished on its surface with large perpen- 

 dicular spines. 



The two terminal disks {disci) are furnished at the mar- 

 gins with deep notches ; the teeth thus formed have a per- 

 pendicular position. 



The actual form of the disk, as well as the number of teeth 

 on each disk, I have been unable to ascertain. 



If we summarize the most important characters of our 

 sponge and compare them with those of Dosilia Baileyi^ it 

 appears that the two sponges must belong to the same genus, 

 but are specifically different. 



These characters are as follows : — 



Dosilia Baileyi^ Carter (/. c. p. 95). 



" Coating, surface smooth. Structure friable, crumbling. 

 Skeleton-spicule curved, subfusiform, gradually sharp-pointed, 

 smooth. Flesh-spicule minute, curved, fusiform, gradually 

 sharp-pointed, covered with erect obtuse spines throughout, 

 extremely small towards the extremities, and extremely long 

 and perpendicular about the centre of the shaft. Stato blasts 

 * See Dybowski, /. c. tab. i. tigs. 3 & 5. 



