18 F. A. SMITT, 



For the genus Biflustra, of course, the outer form of the colony must go out of 

 the definition, thus embracing both the encrusting and raised forms, of the above- 

 named zooecial constitution. 



Biflustra Lacroixii y ) (Pl. IV, figs. 85- 



This species, although with much hesitation, I place in the genus Biflustra, be- 

 cause, in its most advanced states of development, it seems more and more to approach 

 to the following ones. 



In what I consider to be its first, lowest state of development (fig. 88), it is a 

 thin, glossy, yellow-white shining crust, with the limits between the zooacia scarcely 

 perceptible, with the elliptical area?, distant from each-other, very well-marked through 

 their thickened, granular börder. In the zooecia, covered by their thin, translucent 

 ectocyst, within the area?, the bundle of tentacles and the musculi retractores operculi 

 clearly present themselves through their black colour. 



This was the very uniform constitution of one little colony, growing on a Stegino- 

 porella at 35 fathoms. Another colony, of greater development (figs. 85 and 86), taken 

 at 60 fathoms, showed the zooscia with their area? more densely approximated to each- 

 other, varying from the elliptical (fig. 86) to the more and more regular, quadrangular 

 shape (fig. 85). At the corners of the zooecia sometimes a triangulär (through its cal- 

 cification a little raised) space is left, but never with that stout tubercle represented 

 in the cited figure of Savigny. The ooecia have the same i-spherical shape, repre- 

 sented by that author, except that, curiously, they seem, by his drawer, to have been 

 placed preposterously. 



The colour of this specimen has löst its clearness; yet, through the dusky grey 

 ectocyst, the black tentacles and retractor-muscles of the operculum still are visible. 



As to the size of this species, once I measured the breadth of one operculum to 

 abouth 0,16 mm.; the breadth of another was about 0,18 mm. 



Small and few as are these colonies, they do not give any idea of a higher differ- 

 entiation; but the above-named changes of the zooecial form seemingly point out the 

 direction of the development, as going towards the typical constitution of a Biflustra. 



Besides the above-named specimens, Pourtales has taken another colony, groAving 

 on the inside of a dead shell, at a depth of 13 fathoms. 



Biflustra denticulata 2 ) (Pl. IV, figs. 89 — 91). 



The synonyms, cited below, will show that I leave the cpiestion yet undecided, 

 as to the identity of this form with the old-known species, which is so commonly 



J ) FLustra Lacroixii, Acd., Sav., Descr. de 1'Egypte, Zool., Pol)pes, pl. 10, fig. 9; Busk, p. p. (Mem- 



branipord) Cat. Brit. Mus., Polyz., p. 60, pl. LXIX. 



? Flustra puelcha, D'Orb., Voy. cl. VAmér. mer., Polyp, p. 18, pl. VIII, figs. 15, 16; Id. (.Biflustra) 



Pol. Franc, Terr. Uret., vol. V, p. 244; (Beptoflustra), 1. c, p. 328. 

 2 ) ? Flustra tuberculata, Bosc, Vers, vol. III, p. 118; Busk (Membranipora) Quart. Journ. Micr. Se, vol. VI, 



p. 126, Zooph., tab. XVIII, fig. 4; Id., Crag Polyzoa, p. 30, tab. II, fig. 1. 



