ART. 21 CYCLOSTOMATOUS BRYOZOA CANU AND BASSLER 85 



Family ASCOSOECIIDAE Canu, 1919 



Genus LATEROCAVEA D'Orbigny, 1853 



1853. Laterocavea D'Orbigny, Pal^ontologie frangaise, Terrain Cretac^, vol. 5, 

 p. 933. 



Original diagnosis. — "Colonie fixe par sa base, d'oii partent des 

 rameaux tres comprimes, divises par des dichotomisations siir le 

 meme plan et representant un ensemble flabelliforme dendroide. 

 Cliaque branche comprimee est pourvue, sur ses deux faces larges 

 de lignees transversales espacees, composees d'une seule rangee de 

 cellules tubuleuses; entre ces lignees sont de nombreux pores inter- 

 mediaires. Sur le cote etroit des branches sont des surfaces tres. 

 grandes, couvertes seulement de pores opposes epars, ou par lignes 

 longitudinales bifurquees dans des sillons." 



Diagnosis. — The zoarium is dichotomous and formed of compres- 

 sed fronds. The tubes are oriented toward two cellular faces; they 

 are cylindrical, with peristome; their gemmation is axial around a 

 central tube. They are separated by parietal mesopores. The two 

 noncellular sides are formed only of parietal mesopores. The ovicell 

 is placed on a side with mesopores. 



Genotype. — Laterocavea dutempleaTm D'Orbigny, 1853. Cretaceous. 



LATEROCAVEA DUTEMPLEANA D'Orbigny, 1853 



Plate 15, figs. 1-6 



1853. Laterocavea dutempleana D'Orbigny, Pal^ontologie frangaise. Terrain 

 Cretac6, vol. 5, p. 933, pi. 772, figs. 7-10. 



We have discovered some excellent specimens of this remarkable 

 species, which have permitted us to study the detailed structure. In 

 transverse section the tubes are round and grouped around a central 

 tube. The parietal mesopores have very thick walls; they form an 

 exterior zone, regular, enlarged laterally. 



In longitudinal section the tubes are cylindrical, short, somewhat 

 narrowed at their base. The gemmation is axial around a central 

 tube, which ramifies at the dichotomisations. In their terminal 

 recurved portion the tubes are separated by parietal mesopores, with 

 thickened walls. 



In meridian section the axial tubes have the lozenge-shape derived 

 from their orientation toward the broad sides. The lateral tubes 

 are aborted and emit only parietal mesopores much longer than the 

 others. 



In tangential section the orifices are elliptical, often adjacent later- 

 ally, and separated in the longitudinal direction by irregular groups 

 of 4 or 5 mesopores. 



