MISCELLANEOUS. 65 



long bristly processes are entirely wanting, or wherein the marginal spines 

 are developed with less regularity. The discrepancies apparent in such 

 diminutive objects may be deceptive. 



A specimen, investing the Tubularia indivisa, is represented, fig. 19. 

 Portion enlarged, fig. 20. One investing the Sertidaria (Campanularia) 

 djchotoma, is seen, fig. 21. Portion of the surface, enlarged, fig. 22. 



Plate XVIII. Fig. 16. Membranipora pilosa investing a slender substance. 



1 7. Portion enlarged, shewing the hydrse and bristles. 



18. Hydra. 



19. Membranipora pilosa investing a stem of the Tubularia 



indivisa. 



20. Portion of the same, enlarged. 



21. Specimen investing the Sertidaria (Campanularia) di- 



chotoma, enlarged. 



22. Part of the surface of the same, more enlarged. 



Of the preceding figures, 17, 18, 20, 21, 22, are en- 

 larged. 



Tubipora serpens.— Plate XVIII. Figs. 11, 12, 13, 14, 15.— This 

 is a diminutive, calcareous, tubular zoophyte, of which the nature seems 

 to be yet but indifferently understood. 



When recent, it is of purplish colour, gradually refining into pure 

 white, like many other zoophytes. 



It appears under two different aspects, as a substance with tubular 

 extremities, either adhering by a contracted basis to some foundation, or 

 rising by ramifications from that foundation. The latter form is the more 

 frequent. 



These ramifications consist of transverse rows of tubuli, composing a 

 common wall by their approximation, there being seldom any distinct 

 separation of them. The number in a row seems indefinite, and apparently 

 depending on the form, age, and dimensions of the specimen, Plate XVIII. 

 fig. 11. The same enlarged, fig. 12. Another specimen, fig. 13: en- 

 larged, 14. Another specimen natural size, fig. 15. 



