18 PROCEEDINGS OF THE NATIONAL, MUSEUM. vol.61. 



TRIGONOECIA MICHELINI Blainville, 1830. 



Plate 2, figs. 12, 13. 



1896. Diastopora michelini Gregoet, Catalogue of the Jurassic Bryozoa in 

 the British Museum, p. 124, pi. 7, fig. 2 (cites bibliography and geologic 

 distribution). 

 1898. Diastopora micJielini Canu, Etudes sur les ovicelles des Bryozoaires 

 du Bathouien d'Occaignes, Bulletin Soci6t§ geologique de France, ser. 

 3, vol. 26, p. 277, figs. 10, 11. 



Diameter of aperture 0. 13- 0. 14 (max.=0. 17) mm. 



Measure- J Diameter of peristome 0.17- .21mm. 



ments.—) Diameter of zooeciiim .21- .28 mm. 



Distance of peristomes .75- .85 mm. 



Structure. — In longitudinal section the tubes are rather short, cylin- 

 drical, with triparietal gemmation on a median lamella (= basal) ; 

 their inferior part is narrowed according to the rule in this case. 



In transverse section the tubes are polygonal with thin adjacent 

 walls. As the greater part of the fronds are undulated, the median 

 lamella is never rectilinear and one side is always thicker than the 

 other. The tubes adjacent to the median lamella are smaller than 

 the others because they represent the inferior part of the tubes. 



It will be observed in the present article that all the Diastoporas of 

 the older authors have not this structure and that their ovicells are 

 not at all identical. Diastopora is only a zoarial form and by no 

 means a natural genus. 



Occurrence. — Jurassic (Bathonian and Bajocian) : Ranville (Cal- 

 vados), Occaignes (Orne), etc., France. 

 Plesiot7/pe. —Csit. No. 68911, U.S.N.M. 



TRIGONOECIA VERRUCOSA Milne Edwards, 1838. 

 Plate 4, fig. 5. 



1898. Diastopora verrucosa Canu, Etude sur les ovicelles des Bryozoaires 

 du Bathonien d'Occaignes, Bulletin Soci^te geologique de France 

 ser. 3, vol. 26, p. 269 (bibliography). 



Diameter of aperture 0. 14 mm. 



,, ^ Zooecial diameter .20 mm. 



Measurements. — t^- ^ , , 



Distance between peristomes .60mm. 



Separation of peristomes .70 mm. 



Structure. — The measurements are a little different from those of 

 Canu, 1898, but they are close enough. In the Berenicea growth 

 forms it is impossible to obtain measurements in absolute agreement. 



The ovicell is globular, triangular, transverse, wrinkled trans- 

 versely. The oeciostome is very long (0.16 mm.) ; it is supported on 

 an ordinary tube. Its diameter is small (0.10 mm.), and its orifice 

 measures 0.06 mm., as in all the species of this genus. 



