268 



The ooecia (figs. 1, 3), which are only formed by a single zooecium, are free 

 with the exception of a small proximal portion of the endoocecium formed by a 

 part of the zooecium's frontal wall distal to the aperture. They are strongly arched, 

 not far from being globular and consist of two calcified layers of which the thick 

 ectoocecium about the middle is provided with a low, girdle-shaped, proximally 

 convex impression covered by a chitinous plate of the same form. Within the 

 impression is seen an irregular series of mostly elongate pores separated by thick 

 cylindrical pillars. In the ooecia-bearing zocecia the aperture is on each side pro- 

 vided with a small rounded protuberance (fig. 3) distally to the opercular ridge, 

 and the aperture of the ooecium can be closed by the operculum. 



Some colonies of this interesting species have been found incrusting shells at 

 Koh Kram, Siam, at a depth of 30 fath. by Dr. Th. Mortensen. 



Our Zoological Museum possesses a small colony of another variety from Port 

 Phillip Heads, which has a nearly circular Tata-shaped ancestrula, surrounded 

 by 12 marginal spines (fig. 4). The spines are not only much longer and stronger 

 than those in the variety from Siam but are divided into ca. 8 internodes. The 

 pore-bearing impression of the ooecium is almost circular and within it is seen 

 a number of scattered pores. 



In the form figured by Savigny the ooecium seems to be provided with scat- 

 tered pores, separated by a number of parallel longitudinal ridges. 



Before being able to make a thorough examination of the present species, I 

 have set forth the supposition in the morphological part that it might belong to 

 the Suborder Anaska and the reason for this supposition was chiefly the lack of 

 the ci'oss-bar in the vibracula together with a certain likeness to Megapora ringens. 

 Later I have been able to examine some good colonies from Siam, and having 

 seen that the operculum is in connection \^ith a compensation-sac I cannot longer 

 maintain this view, holding however at the same time that this genus has its 

 nearest relatives in the division Malacostega. This appears not only from the lack 

 of the cross-bar, but also from the presence of marginal spines surrounding a 

 great deal of the calcified frontal wall. While a great number of the Ascophora 

 are provided with marginal spines surrounding the anter of the aperture (»oral 

 spines«), with the exception of Crepidacantha we find marginal spines placed in 

 the circumference of the frontal wall only in the division Malacostega and only in a 

 few ancestrulse for instance in those of Chaperia spinosa^ and Microporella ciliata^ 

 do we find such spines together with a well-developed cryptocyst. Though the spe- 

 cies of the genus Megapora are provided with a completely calcified frontal wall 



> 45, PI. 5, fig. 3. ^ 19, p. 334, PI. 15, fig. 6. 



