•im 



Haplopoma n. g. 



The zod'cia with scattered pores, a simple operculum and a median ascopore 

 as an orilice lor the compensation-sac. The oa'cia covered by kenozoa'cia with 

 scattered pores. No avicularia. 



H. impressum Audouin. 

 Microporella impressa Hincks, Hrilish Marine Polyzoa, pag. 214, 



PI. XXVI, (igs. y— 11, PI. XXIX, iigs. 10, 11. 

 (PI. XXII, ng. 9a-<)b, lOa-lOe, I'l. XVIII, lij^. ll a). 



While Hincks and all later systematic authors have referred this species to 

 the genus Microporella, wilh the species of which it agrees in the possession of a 

 median ascopore, a simple operculum and pore-chambers, Barrois' in his greal 

 woik on the larvae has rightly recognised its relationship to Hippothoa hijitliim 

 and called attention especially to the great similarity of their larva', which be- 

 long to rather a peculiar type. He is however wrong in referring both these 

 species to the same genus {Mollia). 



The supposition, expressed on several former occasions, that the median asco- 

 pore has arisen by a conslriclion from an original sinus is also conlirmed in Ihis 

 species, and Waters^ has already called attention to the fact, that the primary 

 zoo'ciuni in //. iinprcssiim (PI. XXII, figs, i) a — 9h) as well as in H. biiniicrnnatitm, 

 Moll (PI. XXII, iigs. 10 a — 10 c) is provided wilh a sinus, which is however both 

 narrower and deeper in the latter than in the former. The primary zoa^ciuni in 

 the laller species is moreover distinguished not only by possessing a curve of 9 

 l)()res, but also by having an oi)erculum (fig. 10 e) similar to that found in the 

 genus Arthropoina, the accessory part of the operculum, corresponding to the 

 sinus, being separated from the principal part by a less strongly chitinized por- 

 tion. This dilferencc in the primary zocrcia also speaks in favour of the opinion 

 maintained by Waters, that H. biimnronatiim, which was formerly considered but 

 a variety of H. impressum, is a dislinci species. 



Genus Trypostega n. g. 

 The zon-cia with scattered jxjres and a compound opercidum. The oo'cia 

 covered by dwarf zoa>cia with scattered pores. No avicularia. 



' 1, p. 171, I>l. '.), fii^s. 1 — 3, IM. Hi, lit;. 2. - ll.V p U. 



