182 



The spicules appear both in the shape of curves and of compasses, but both 

 these forms show a considerable range of variation not only as to dimensions 

 but also in shape. 



The ooecia, which need a closer examination, are very broad. 



The avicularia, generally considerably smaller than the zocecia, have a man- 

 dible in the shape of an isosceles triangle with lateral margins curving outwards 

 a little. The opercular arch has also the shape of an isosceles triangle, and its 

 two curved sides, situated a little inside the lateral margins, meet at the point 

 of the mandible. 



The description of this apparently widely spread and frequently occurring 

 species is based on material from many different localities. The species is ex- 

 ceedingly variable, and as a necessary supplement to the account above I shall 

 here give short descriptions of a number of varieties, which no doubt may be 

 largely increased. 



Var. A. (labiata). 



(PI. VI, figs. 6a-6j). 



Length of zocecia 0,45 — 0,57"""- The aperture measures, the sinus included, about 

 one fourth of the whole length of the zocecium. It has in a greater or smaller 

 number of zocecia a more or less developed, often dentate and longitudinally 

 furrowed, somewhat projecting lip, which entirely or partly fills the original 

 sinus. The two adoral areas are well developed, frequently with acropetal spines, 

 seldom without. The margins of the two opesiulse are often spinous, and only 

 the one opesiular outgrowth reaches the basal wall, which it meets in a closed, 

 narrow, tongue-shaped, curved line, pointing inwards and a little proximally. The 

 distal wall of the two lateral recesses is oply provided with a small, sometimes 

 extremely small foramen. 



Spicules. Length of curves varying between 0,026 and 0,186™™- and that of the 

 compasses between 0,039 and 0,093™™-; but besides the variation found within the 

 same zocecium both with regard to dimensions and form, some variation in both 

 respects is also found in colonies from different localities. The vai-iation is great- 

 est in the curves, and they reach their maximum in the colony from the Formosa 

 Channel, in which they also have a more even and less sharp curvature. 



Localities: Paumben, India (Fristedt), covering algse from a depth of 1—2 

 fathoms; Singapore, India (Consul S. Gad), covering algse from low water; the 

 Formosa Channel, lat. 23° 20' N., long. 18" 30' E., depth 17 fathoms, (Andrea). 

 This last form, which is without spines and in which the above-mentioned lip 

 attains its highest development and occurs at the earliest stage, is fquud ip two- 



