The Bryozoa of the Tortugas Islands, Florida. 201 



The ovicell is globose, at first smooth, but later tuberculate like the 

 zooecium; on either side at the widest part and near the base is a rounded 

 thin area appearing membranous; in complete calcification the peristome 

 rises over the front of the ovicell and fuses with the outer layer, leaving a 

 thin, somewhat triangular area on the front. 



One colony at 18 fathoms, incrusting a shell with a single layer of 

 zooecia. 

 Rhynchozoon solidum n. sp. (Figs. 10, 11, and 12.) 



Fig. 10. — Rhynchozoon solidum n. sp. Enlarged, showing primary aperture, spines, two 



pairs of denticles, and the beaded vestibular arch. 

 Fig. II. — The same. Operculum. 

 Fig. 12. — The same. Fully calcified, showing avicularium, peristome, and ovicell. 



Zooecia small, little swollen, rather broad, closely set in a continuous 

 crust, thick-walled, the surface smooth or irregularly traversed by very 

 fine lines. As a rule only three pores are seen, one at the posterior margin 

 and the others on either side of the orifice at the margin. Orifice evenly 

 rounded, a little broader than long, with a rounded sinus in the proximal 

 border. This sinus is really double, being formed by two sets of denticles, 

 the lower pair equal in size and inclosing a semicircular sinus much like 

 that of many Schizoporellas. Immediately above them is another pair of 

 denticles, more pointed and a little longer than the lower ones, and often 

 one of them is a trifle larger than the other; they are turned inward more 

 than the lower pair, so as to inclose a narrower and more nearly circular 

 sinus. The operculum is well chitinized, yellowish in color, the dots showing 

 attachment of muscles situated nearly half-way from the circumference 

 toward the center. Through the operculum can be seen a beaded vestibular 

 arch very similar to that figured by Levinsen (1909, pi. xxiii, fig. 4^) for 

 R. angulatum. In young cells there are four short, stout spines about the 

 anterior margin of the orifice. The peristome is high and thick, extending 

 upward and forward on the sides into thick, lappet-like processes, usually a 

 little unsymmetrical ; posteriorly the peristome extends upward and over 

 the orifice in the form of a broad mucro, though sometimes this is but little 

 developed. 



Small avicularia, sometimes a pair, frequently only one, are placed 

 posteriorly not far from the margin, with the triangular beak pointing 

 laterally. 



