SIDONOPS ANGULATA. 



39 



somewhat different even in most closely related individuals; and finally as 

 the difference in the subcortical triaenes, which is the only valid difference of the 

 less exposed internal parts, is, as a comparison of the cladomes of these triaenes 

 (Plate 26) shows, not very great; it appears advisable to place these four 

 sponges in one and the same species, with three varieties within this species. 



DIFFERENCES BETWEEN THE VARIETIES OF SIDONOPS ANGULATA. 





Var. megana 



Var. niicToana 



Var. orthotriaena 



Colour 



white, yellowish, reddish 

 brown. 



dirty white, purple-brown. 



brownish white. 



Stout, choanoso- 

 mal amphioxes 



2-3.7 mm. long, 40-72 /( 

 thick. 



1.8-2.8 mm. long, 20-52 /( 

 thick. 



1.6-2.5 mm. long, 20-70 /< 

 thick. 



Slender, dermal 

 amphioxes 



not numerous; 4.2-9.5 

 mm. long, 18-34 /i thick. 



very abundant; 5.5-7 mm. 

 long, 10-22 /( thick. 



not numerous; 2.9-4.5 

 mm. long, 5-17 /( thick. 



Styles (stylc-deri- 

 vates) 



2.1-2.5 mm. long, 60-100 

 /( thick (not found in the 

 massive specimen). 



as in the lobose specimen 

 of var. megana. 



as in the lobose specimen 

 of var. megana. 



Plagio- or ortho- 

 triaenes 



plagiotriaenes. 

 rhabdonie 1.6-2.8 mm. 

 long, 50-82 /( thick; 

 clades 330-700 /< long; 

 clade-angle 92-104°, av- 

 erage 102.15°. 



plagiotriaenes. 

 rhabdomes 1.5-2.6 mm. 

 long, 50-77 /< thick; 

 clades 380-580 n long; 

 clade-angle 91-112°, av- 

 erage 105.6°. 



orthotriaenes. 

 rhabdome 2-2.35 mm. 

 long, 47-78 /< thick; clades 

 380-500 /( long; clade- 

 angle 91-98°, average 

 93.7°. 



Anaclades 



ana triaenes. 



rhabdome long, 7-39 /( 

 thick; chides 45-210 /( 

 long; clade-angle 27-66°, 

 average 46°. 



anatriaenes and anadi- 

 aenes. 



rhabdome shorter, 10- 

 18 /( thick; clades 30-.50 /< 

 long; clade-angle 50-62°, 

 average 47°. 



anatriaenes. 



rhabdome long, 14-18 /< 

 thick; clades 33-80 /! 

 long; clade-angle 43-54°, 

 average 48°. 



Oxyasters and oxy- 

 sphaerasters 



1-23 rays; 11-64 /( in 

 total diameter. 



1-18 rays; 15-54 /i in 

 total diameter. 



2-20 rays; 13-60 /( in 

 total diameter. 



Strongylosphaer- 

 asters 



3-20 more cylindrical rays ; 

 14-26 /I in total diameter. 



10-17 more conic rays; 

 19-24 /( in total diameter. 



1-17 more cylindrical 

 rays; 17-24 in total 

 diameter. 



Sterrasters 



all regularly ellipsoidal ; 

 10.5-122 11 long; 90-114 /( 

 broad, 70-86 /( thick. 



all regularly ellipsoidal; 

 85-97 /( long, 75-90 /( 

 broad, 57-65 /t thick. 



besides the regular ellip- 

 ■soidal also rhomboidically 

 distorted ones, 90-111 ji 

 long, 80-94 /( broad, 65- 

 79 /( thick. 



The structure of the skeleton and the canal-system with its cribriporal 

 afferents and its uniporal efferents clearly show that this species belongs to 

 Sidonops. None of the previously described species either of Sidonops or 



