& 



FLORIDAN BRYOZOA. 19 



growing on the Sargassum fluitans. Yet the differences, for the most part, reduce them- 

 selves to the size of the zocecia and to the different degrees of calcification. 



The Floridan specimens, growing on dead shells and corals, in their younger 

 zocecia remind us of Bifl. Lacroixii, as they are covered by a transparent, glossy ecto- 

 cyst and have their margins in the same manner granulated. But very soon the area 

 is encroached, proximally and laterally, by that internal calcareous lamina of marine- 

 bluish hue, prickled with white pores and irregularly prolonged, internally, into den- 

 ticles (tig. 91), which have given this Biflustra its name. The secondary area, thus 

 constituted, varies much in its shape, according to the development of the lamina and to 

 the outer form of the zooecion, which is depending on the more or less regular growth 

 of the colony. Very coinmonly, at the one of the proximal corners, the area is more 

 encroached upon than at the other; but more and more, in the older zocecia, it ap- 

 proaches to the rounded rectangular form, occupying about half the length of the prim- 

 ary area, which form is to be considerecl as typical for the species. At the same 

 time the calcification is going on: the pores in the named lamina are to be filled, and 

 this becomes granular by warts, the dénticles on the margin of the secondary area 

 for a good part dissappear, and, at the proximal corners of the zocecia, the rounded 

 tubercles are developed, just of that form described; in the Crag Polyzua, by Busk. 

 Yet, these tubercles in no wise are constant, as seen form the figures 89 and 90, which 

 are taken from different parts of the same colony. 



In comparing this form, then, with the true Biflustra tuberculata, we find all the 

 same parts, in the same manner, but in different degrees, developed. For on the B. 

 tuberculata, also, I have seen the above-named lamina, with its pores, though not so 

 much developed, intruding on the proximal part of the primary area; and the dénticles, 

 also, are to be seen, but shorter and closer together. The tubercles, as already re- 

 marked by Busk, on the B. tuberculata are more developed, higher, very often crooked, 

 and, in accordance with their greater size, proportionately to the breadth of the prox- 

 imal end of the zooecion, of course they must be more nearly approximated, especially 

 at the doubling of the zocecial rows. The Avalls of the zocecia, also, on the B. tuber- 

 culata, proportionately to the size of the individuals, are higher, and, like the tuber- 

 cles, they are white, instead of being greyish or, in the microscope, of a bluish hue. 

 As to the respective size of the two forms, among all variations, for the following 

 measures I have chosen two zooecia, seemingly of the most common and regular shape: 



B. denticidata. B. tuberculata. 



Length of the zooecion 0,58 mm. 0,44 mm. 



Breadth » » » (in the middle) 0,28 » 0,20 >> 



» » » operculum 0,1 » 0,1! » 



? Flustra membranacea, Esper, Pflanzenth., Flustra, tab. V (excl. descript); Wood (Membranipora) AnD. 

 Mag. Nat. Hist., vol. XIII, p. 20 (sec. Busk). 



? Flustra tehuelcha, Fl. inca, Fl. Isabelleana (?), Fl. peregrina, D'Orb., Voy. d. VAmér. mer., Polyp., 

 pp. 17 et 18, tab. VIII, figg. 10—24, tab. X, figg. 1—3; Id. (Reptoflustra) Fal. Franc, Ten: Gret., 

 vol. V, pp. 328 et 329. 



? Membranipora telacea, Busk, Oat. Brit. Mus., Polyz., tab. LVIII, fig. 6. 



Membranipora denticulata, Busk, Quart. Journ. Micr. Se, vol. IY, p. 176; Zooph., tab. VII, figg. 1 et 2 



