30 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 76 



tremocyst. The median avicularium is triangular, acuminate, the 

 beak below, adjacent to the peristome. The apertura is large orbicu- 

 lar with a simply concave proximal border ; the peristome is salient, 

 indented in front by a broad, round rimule. The ovicell is large, 

 globular, salient, buried in the distal zooecium, perforated by small 

 pores, and margined by a large salient collar. 



Measurements. — 



fAfl5=0.14 mm. [Z(Z= 0.65-0.60 mm. 



Aperturaj ?^= o.l4 mm. ^ooecia | ^^=. 0.30-0.40 mm. 



Structure. — This species is very deceiving. Without the prepara- 

 tion of the operculum and the interior we would have classed it in 

 SchizoTnavella. It is only the peristomice which has the schizoporel- 

 lidan form ; the form of the apertura is different. 



Certain colonies have a curious form of successive palm-shaped 

 branches, as in Berenicea. There are four uniporous septules. As in 

 other genera of Smittinidae, the operculum is very thin and without 

 any ornament. 



Affinities. — The closest species is Lejjralia pachnoides MacGilli- 

 vray, 1886, of Australia, but the present form differs in its sub- 

 orbicular (not subelliptic) aperture and in the presence of numerous 

 frontal granulations. 



Biologij. — Our specimens were in reproduction on April 7, 1888. 



Occurrence. — Galapagos Islands, D. 2813 and D. 2815. 



Gotypes.—C^t. Nos. 8500, 8501, U.S.N.M. 



Family RETEPORIDAE Smitt, 1867 



DIPLONOTOS, new genus 



Greek ; diplos, double ; notos back ; referring to the double dorsal of the 

 zoarium. 



Reteporidae in which the two faces of the reticulated colony are 

 covered by vibices. The zooecia are arranged on the edges of the 

 branches in the fenestrae. 



Genotype. — Diplonotos costulatum^ new species. Recent (equa- 

 torial Pacific). 



The reticulated colony and the presence of the vibices have caused 

 us to class this genus in the Reteporidae. In reality we are ignorant 

 of the ovicell, the operculum, the aperture, and the frontal 

 structure. 



DIPLONOTOS COSTULATUM, new species 



Plate 5, Figures 1-i 



Description. — The zoarium is free, reticulated, composed of prin- 

 cipal branches bearing pinnules; the latter often join the neighbor- 

 ing branches forming a kind of fenestrae; the branches are sub- 



