44 F. A. SMITT, 



With these characters, as will be seen in comparing it with the figures given by 

 Savigny, the Hippothoa pes anseris presents no other discrepance from the Hippothoa 

 Dutertrei, than the forked vibraculum, provided with an interradial membrane, thus 

 resembling, in miniature, one foot of a goose. In comparing the Hippothoa Dutertrei 

 with the description and figures of the Hipp. vulgaris given by Busk (Quart. Journ. 

 Micr. Se, 1. c.), the most essential difference seems to consist in the more distal place 

 of the vibracularia of the first-named form, what difference, as in other forms we know 

 the variability in this respect, scarcely will be enough for the specifical distinction, 

 although these forms, when typically developed, readily will be distinguished. The 

 fine denticulation of the proximal margin of the zooecial aperture of the Hippothoa 

 pes anseris, which, very possibly, has escaped the observation of Savigny, has no other 

 significance, I think, than that of a variety of calcification. At the proximal corners 

 of the zooecial aperture, a lateral sinus sometimes is to be found, just alike what we 

 have seen on the Hippothoa porösa. 



The Hippothoa pes anseris was taken by Pourtales in two small colonies, gro- 

 wing on a Nullipora, West off Tor tu gas. 



Not very far from the Hippothoa spongites, though, by its perpetually more open 

 median sinus of the zooecial aperture, well distinguished from it, the 



Hippothoa Isabelleana ') (Pl. VIII, tigs. 166—168) 



.is to be placed. 



Of this species Pourtales has sent me two varieties, whose differences, however, 

 with all reason will be accounted for by their different degrees of colonial development. 



The first variety (fig. 168) Avas growing in one single layer of whitish and yellowish 

 hue on Oculina and Nullipora, at the depth of 42 fathoms. It is in a pretty bard 

 degree of calcification; thus the pores on the convex front-side of the zooecia, and 

 still more on the rounded, infiate ooecia, sometimes scarcely are discernible. The zooe- 

 cial aperture, with a breadth of about 0,1* mm., secondarily raised into a moderately 

 high rim, is of a semielliptical or semicircular form, with a semicircular sinus in the 

 middle of the straight proximal margin. The avicularia are wanting. 



The other variety was found growing in the depth of 17 fathoms, in a consi- 

 derably greater and more compound colony, composed of several concentric layers, of 

 a purplish blue tint, around an axis of foreign matter, probably a branch of a coral 

 (fig. 167 and a). Here (fig. 166) the acute, lateral avicularia, at the side of the zooe- 

 cial aperture, are very constant, and the pores on the front side are great and con- 

 spicuous, usually deeply sunken in the secondary thickening of the wall. The zooecial 

 aperture, with a breadth of about 0,iö mm., in its developmental changes, presents the 

 median sinus in the proximal margin varying from a broad concavity to a shorter, 

 semicircular, form. Internally, at last, it is encroached upon, proximally, by a broad, 

 transverse plate. 



') Escharina Isabelleana, B'Okb., Voy. cl. VAmér. mér., Tom. V, Part. 4, Zooph., Divis. 1, Bryoz., p. 12, 

 tab. IV. fig. 13 — 16; lo. (Reptoporina) Pal. Franc, Terr. Gret., vol. V, p. 442. 



