70 PROCEEDINGS OF THE NATIONAL MUSEUM vol.72 



Tif j^ r\ ■ [^0 = 0.12 mm. 



Measurements. — Opesmm , ^,^ 



Uo = 0.15 mm. 



ry . [is = 0.40 mm. 

 Zooecia , ^ „_ 



1/2 = 0.30 mm. 



Structure. — The opesium is trifoliate; the two lateral condyles 

 serve as a support to the opercular valve. The latter is very simple 

 and analogous to that in the Membranipores. The proximal portion 

 of the opesium which it does not cover probably serves as a passage 

 for the opesiular muscles, but we still have no material proof of their 

 presence and the genus could just as well be classed next to Amphi- 

 hlestrum. 



The zooecia are disjoined; a single point of junction unites them 

 to each of the adjacent zooecia. On the inferior face they are sur- 

 rounded by a series of small nonadjacent tuber- 

 osities. According to Waters, 1879, they serve 

 as attachments of very small radicular threads. 

 The ovicell is hyperstomial, salient, globular, 

 closed by the opercular valve. 



Fig. 10.— MOLLIA PATEL- a /r -j- r\ •,, , r^w<-. • i ,•r'■^^^ 



LABIA smitt, 1S73. AJfinities. — Smitt, 1872, identmed his species 

 Drawing OF a zooe- ^^^-^ Eschara vatellaria Moll, 1803, but it differs 



CIUM, X 85, SHOWING ... 



THE apeetueal scle- from it In its more closely arranged adjacent zoo- 

 rite SOMEWHAT EE- g^j j^g much smallcr ovicells, and in the two ope- 



MOVED FEOM THE . ' ' '^ 



MURAL RIM AND slular condylcs placcd higher. The best figure of 

 SUPPORTED WITH THE ^yf^ipg spccics givou by Watcrs iu 1879 has served 



OPERCULAR SCLERITE ON r- » ^ 



THE TWO 0PE3IAL CON- US for comparisou. In the Gulf of Mexico, this 

 °^^^^ species has been found only on nullipores. 



Occurrence. — Albatross Station D. 2405, Gulf of Mexico; 28° 45' 

 00" N.; 85° 02' 00" W.; 30 fms.; gray sand, broken coral. Florida, 

 58 meters (Smitt). 

 Plesiotype.— Cat. No. 7559, U.S.N. M. 



Family ARACHNOPUSIIDAE Jullien, 1888 



Genus EXECHONELLA Canu and Bassler, 1927 



EXECHONELLA PUMICOSA, new species 



Plate 14, Figure 1; text Figure 11a 



Description. — The zoarium encrusts shells. The zooecia are dis- 

 tinct, separated by a deep furrow, very large, oval, somewhat elon- 

 gated; the frontal is convex, very porous; each pore (or lacuna) is 

 surrounded by a salient peristome. The aperture is large, suborbicular, 

 a little elongated or a little transverse, formed of a large anter 

 separated from a smaller poster by two lateral indentations; two 

 small lamellae arrest the movements of the operculum; the peristome 

 is thick salient. One of the peripheral pores is transformed some- 

 times into a small round avicularium. 



