390 Transactions of the Society. 



XXIV, — On the Occurrence of Recent Reteropova. 

 By Arthur Wm, Waters, F.G.S. 



(Bead Uth May, 1879.) 



Plate XV. 



In looking tlirough some of the British Museum recent Bryozoa, I 

 several times came across portions of round branches from the 

 neighbourhood of Japan, and upon examination some were seen to 

 be Myriozoum ; but the structure of others, similar in form, was 

 upon first sight a puzzle, for broken sections seemed to show trans- 

 verse markings like septa, so that I was in doubt as to what this 

 might be, and it was necessary to make transparent sections before 

 the appearance was explained, but then the tubular cyclostomatous 

 nature was quite clear, and it was interesting to find a Cheilosto- 

 matous {Myriozoum subgracile d'Orb.) and a Cyclostomatous 

 Bryozoon from the same locality, so similar in habit that they were 

 placed together as the same species, not in one case only, but in 

 several. 



As is the case in all Cyclostomata, the shell-walls are perforated 

 by small holes, and the shell thickening between these holes gives 

 sometimes a beaded appearance (Fig. 4) to a section of a cell- wall ; 

 and it is to the irregular thickening of the shell causing well-hke 

 depressions round these holes that the peculiar appearance of 

 transverse lines is due. 



Mr. Busk, in the 'Crag Polyzoa,' page 122, speaks of partial 

 transverse nearly equidistant septa in Heteropora, and Mr. J. 

 Haime figures most distinct septa in his H. pustuhsa* These 



EXPLANATION OF PLATE XV. 



Fig. 1.— Heteropora pelliculata, nsLtm&l size. (The upper branches are drawn 

 slightly too long.) 



Fig. 2.— Longitudinal section of ditto, x 25. (This is drawn with the growing 

 end downwards, and the structure is perhaps shown better in consequence.) 



Fig. 3. — Transverse section of ditto, x 25. 



Fig. 4. — Portion of same, magnified fifty times. 



Fig. 5. — Operculum of Myriozoum subgracile d'Orb., X 85. 



Fig. 6.— Operculum of Cellepora (Fig. 8), X 85. 



Fig. 7. — Surface of Heteropora pelliculata; b, portion with the thin covering 

 removed. 



Fig. 8. — Cellepora from Australia. 



Fig. 9. — Heteropora ccrvicornis d'Orb. 



Fig. 10.— Surface of ditto. 



Fig. 11. — Ditto, with covering removed. 



* ' Mem de la Soc. Ge'ol. de France,' ser. 2™e^ vol. v. pi. xi. The name H. pus- 

 tulosa was employed by Haime five years previous to the publication of the 'Crag 

 Polyzoa,' and therefore the same name given by Mr. Busk as a new species will 

 require to be changed. Haime's specific name jmstulosa had been employed by 

 Miclielin and d'Orbigny for his species, though the generic name they used waa 

 Ceriopora. 



