230 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



There are no processes on the firm test, and its surface is quite free 

 from denticulation. The oral apertures of the zooids are only slightly 

 sunken (fig. 17). 



The zooids are longer than high, averaging 3 mm. in length, 2.5 mm. 

 in height. The oral chamber, while distinct, is very short; some- 

 times it is quite lacking. The cloaca is also short, never exceeding 

 about one-fifth the length of the branchial basket. 



In details of anatomy this form very much resembles the preceding 

 one. The branchial basket, however, is longer than high, and con- 

 tains more stigmata and supporting bars. On each side there are 

 from 14 to 15 longitudinal bars (or rarely 16), and 27 to 30 rows of 

 stigmata. The dorsal languets number from 5 to 7. As has pre- 

 viously been described forP. veriicillatum, so in this form, the endostyle 

 is rather strongly and evenly curved; but in this species it is, in addi- 

 tion, slightly shorter than the branchial chamber. In the species to 

 be described next this shortening is even more marked. There is 

 nothing peculiar in the organization of the digestive tract. It appears 

 narrow; the intestine is sharply bent upon itself. Ordinarily the 

 cloacal muscles lie opposite the stomach — one on either side of it. 



This species also is protogynous, that is a preponderance of indi- 

 viduals in the colony show a protogynous condition. The testis is 

 a rather compact and roughly hemispherical body, consisting of 

 about 15 lobes. When mature it lies in a distinct evagination of the 

 postero-ventral body wall, and it may at this time attain to a con- 

 siderable size (0.7 mm. in diameter). The egg usually develops 

 somewhat earlier than the testis ; advanced embryos, after becoming 

 detached from the body wall of the parent, complete their develop- 

 ment in the right peribranchial space. Occasionally these may be 

 found in the left peribranchial chamber, or in the cloaca. 



Distribution. All of our specimens of P. hybridum were collected 

 in the western Pacific Ocean, in Philippine waters, by the Albatross 

 during the years 1907-1910, at the following stations: 



D. 5238, Port Lambajon, east coast Mindanao; May 12, 1908; 380 

 fathoms; surface temperature 86° F.; surface density, 1.02453; two 

 specimens; Cat. No. 6493 U.S.N. M. 



D. 5320, China Sea, vicinity of Formosa; Nov. 5, 1908; 1,804 

 fathoms; surface temperature, 80° F. ; 11 specimens; Cat. Nos. 6470 

 (Holotype) and 6408 (Paratypes) U.S.N.M. 



D. 5157, Legaspi Light, east coast of Luzon; June 7, 1909; 146 

 fathoms: surface temperature, 85° F. ; two specimens; Cat. No. 6484 

 l.S.X.M. 



D. 5158, Legaspi Light, east coast of Luzon; June 7, 1909; 200 

 fathoms; surface temperature, 85° F.; one specimen; Cat. No. 6486 

 U.S.N.M. 



