ABT. 13 BRYOZOAN FAUNA CANU AND BASSLER 49 



tubes closed by a calcareous lamella with median tul:)ule. The dimen- 

 sions are identical, the colony is also free and pedunculated, and we 

 were able to observe the same concentric striae and the same ovicells. 



The same closures with median tubules are commonly observed in 

 Plagioecia sarnie7isis Norman, 1864; but the tubes are much more 

 slender than in our species. 



It is often very difficult to discover characters really specific in the 

 Cyclostomata, and we do not believe a new species should be created 

 with characters so little different from those assigned by Calvet to 

 his Diastopora lactea. 



Occurrence. — Galapagos Islands, D. 2813. 



Plesioty pes. ~C?it. No. 8525, U.S.N.M. 



Family DIAPEROECIIDAE Canu, 1918 



Genus DIAPEROECIA Canu, 1918 



DIAPEROECIA STRIATULA, new species 



Plate 11, Figures 3-6 



Description. — The zoarium is orbicular and incrusts shells or algse. 

 I'he tubes are indistinct, immersed in a concentrically striated crust. 

 The peristomie is salient, short, very oblique; the orifice is orbicular 

 or somewhat elliptical ; the peristome is thin. The ovicell is a long, 

 transverse, salient sack perforated by tubes, more often placed near 

 the zoarial margin. 



Measurements. — Diameter of orifice, 0.08 mm. ; diameter of peris- 

 tome, 0.12 mm. ; distance of orifices, 0.30-0.40 mm. ; internal separa- 

 tion of orifices, 0.30-0.34 mm. 



Affinities. — This species bears concentric striae like Microecia sub- 

 orhicularis, with tubes closed by a lamella with tubule like Plagioecia 

 sarniensis Norman, 1864, and closely approximated cells as in Diasto- 

 pora congesta Busk, 1875. It is nevertheless distinctly different from 

 these three species in the ensemble of its characters and In its meas- 

 urements. 



If the substratum is very regular, the peristomiec are of equal size ; 

 tliey are on the contrary very irregular if the substratum is irregular 

 and much elongated in the more sheltered parts. This is the rule, 

 moreover, in all the Cyclostomata. 



The basal lamella is broad, very fragile, and is frequently lacking 

 on the dead colonies. 



This species is clearly distinct from Plagioecia lactea Calvet, 1903, 

 not only in the nature of its ovicell but also in the more closely ar- 

 ranged orifices. This form of ovicell perforated by the tubes is rather 

 common both in the recent seas and in the fossils since the Cretaceous. 



61589—29 4 



