550 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



consideration in addition to the very porous nature of the ovicell 

 seems to indicate that the genus would perhaps be better classed in 

 the Horneridae. We have not discovered the ovicell of the present 

 species. 



We have observed a very special case of ramification. The branch 

 is attached exteriorily to the zoarium as if another colony had become 

 affixed there. The base of the branch is formed entirely of epitheca 

 with vacuoles. The physiological reason for this arrangement is 

 unknown; we have already noted it in the fossil species. 



Affinities. — This species differs from Mesonea radians Lamarck, 

 1812, in the presence of a single tube to the fascicle, in the short 

 tubes with transverse and not long peristomies, in the ascending and 

 oblique peristomie and in its undulated shallow dorsal sulci. 

 Occurrence. — 



D. 5151. Sirun Island, Sulu Archipelago; 5° 24' 40" N.J 120° 



27' 15" E.; 24 fathoms; co. S., Sh. 

 D. 5478. Tacbuc Point, Leyte; 10° 46' 24" N.; 125° 16' 30" 

 E.;Sh. 

 Cotypes.—C&t. No. 8404, U.S.N.M. 



Family HORNERIDAE Gregory, 1899 



Genus HORNERA Lamouroux, 1821 



HORNER A PINNATA, new species 



Plate 86, figs. 1-10 



Description. — The zoarium is free, affixed to stones, bryozoa, 

 serpulae and rarely to algae, by a more or less expanded base; the 

 branches are irregular, dichotomous and bear laterally short pinnules 

 very dissimilar to each other. The tubes are distinct, separated by 

 a furrow, little convex, concave longitudinally, ornamented with 2 

 sulci and with 3, 4 or 5 vacuoles; the peristomie is salient and oblique; 

 the peristome is thin, entire or denticulated. The peristomes are 

 always grouped in series of two arranged alternately on each side of 

 the median longitudinal axis. The posterior face of the zoarium is 

 convex and ornamented with a dozen longitudinal sulci at the bottom 

 of which are numerous vacuoles. The ovicell is a large dorsal, very 

 porous sac in which the oeciostome opens on the cellular face. 



Measurements. — Diameter of peristome, 0.10 mm.; distance of 

 peristomes, 0.40; diameter of large branches, 0.90. 



Variations. — The larva affixes itself on very small fragments not 

 in the least connected with the great development of the colony. 

 The base is little expanded and surrounds more or less the sub- 

 stratum. The discoid base is very large when it is fixed to an alga. 

 (Fig. 2.) This base is always identical with the dorsal and is formed 

 of calcareous skeleton marked by deep sulci radiating from the 



