275 



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

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

 mal side. Aviciilaria are very seldom present, but we frecjuently Mnd very 

 small, sometimes rudimentary zoa-cia, which are however provided with an 

 ajjcrture. The zon'cia in the whole of their periphery have small uniporous or 

 few-pored pore-chambers, and the pore-chambers of one zoo?cium not rarely join 

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

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

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

 They are covered either by kenozoa>cia, dwarf zoa^cia or by avicularia. The 

 colonies are incrusting. 



The zooecia have no covering-membrane, and when Calvel' 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, Iiwersiiila, Adeona, Haplopoina, Tiibucellaria, Caliuellia and Onvho- 

 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 ])elween them. Excepting that Jullien^ 

 has found marginal spines in some ancestrulae of HippoUioa-co\onie>i, and lliat 

 Kirkpatrick'' has described a Chorizopora-torm with two pair of spines in the 

 distal end of the zofrcium, 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. Hi neks' 

 calls the small cliambers, wliich in Trijpostegd neimsta are found partly scattered 

 among the zott'cia, partly surrounding the oa>cia, 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 zooecia, especially as except in the genus Haplopoma we lind wilhin the three 

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

 tered among the ordinary zorrcia. 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 Deiuisht have a small chitinized operculum, 

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



' 9, p. KiG. - 45, p. 30. ^ 4<), p. 01.'). ' 2'i, p. •J/d — 1277. 



. 18* 



