275 



Ordinary spines are usually wanting, whereas short wide acropetal spines not 

 seldom appear, partly on each side of the aperture, partly singly on its proxi- 

 mal side. Avicularia are very seldom present, but we frequently find very 

 small, sometimes rudimentary zocecia, which are however provided with an 

 aperture. The zocecia in the whole of their periphery have small uniporous or 

 few-pored, pore-chambers, and the pore-chambers of one zooecium not rarely join 

 short prolongations of the other, by which means two neighbouring zocecia be- 

 come separated by a row of small openings. The ocecia are sometimes situated 

 on zocecia of ordinary structure, sometimes on gonozocecia of a peculiar form. 

 They are covered either by kenozocecia, dwarf zocecia or by avicularia. The 

 colonies are in crusting. 



The zocecia have no covering-membrane, and when Calvet^ talks of a cryp- 

 tocyst in Chorizopora Brongiarti, the reason may be that he confuses it with the 

 compensation-sac, the opening of which in this form needs however a closer ex- 

 amination. The fact is that Chorizopora possesses a simple operculum, but con- 

 trary to all the other genera of the section Ascophora in which this is the case 

 (Microporella, Inversiula, Adeona, Haplopoma, Tiibucellaria, Calwellia and Oncho- 

 pora), it wants an ascopore, and as the proximal margin of the operculum 

 seems to go close up to the corresponding proximal margin of the aperture, there 

 seems to be no room for any opening between them. Excepting that JuUien^ 

 has found marginal spines in some ancestrulse of Hippothoa-colonies, and that 

 Kirkpatrick* has described a Chorizopora-form with two pair of spines in the 

 distal end of the zooecium, ordinary spines are otherwise wanting in this family, 

 whereas in all the four genera, though not in all species and varieties, the hollow 

 expansions occur which I have mentioned in the diagnosis of the family. Hincks* 

 calls the small chambers, which in Trypostega venusta are found partly scattered 

 among the zocecia, partly surrounding the ocecia, avicularia; but as their aper- 

 ture wants the transverse bar found in the avicularia in Chorizopora between the 

 opercular and the subopercular area, I prefer to call them dwarfed or rudiment- 

 ary zocecia, especially as except in the genus Haplopoma we find within the three 

 other genera of the family individuals of different size, form or structure scat- 

 tered among the ordinary zocecia. Thus, in Chorizopora we may find large num- 

 bers of very small chambers mixed with some avicularia, and the round aperture 

 of these chambers seems to be covered only by a membrane, while the corre- 

 sponding chambers in Trypostega venusta have a small chitinized operculum, 

 which is different from that of the ordinary zocecia, but which does not how- 



' 9, p. 166. » 45, p. 30. ' 49, p. 615. * 22, p. 276—277. 



