536 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



caused it to be classified in ScMzoporclla. In 1914, the recognition of the ovicell 

 system obliged Canu to create a new genus in which he classed in addition 

 Mi trarabdotos (Eschnra) polymorphvm Reuss, 1869. 



This species made its appearance in Europe in the uppermost beds of the 

 Priabonian; it does not exist in the bryozoan marl of the Priabonian. Its occur- 

 rence is therefore valuable for the synchronism of the American formations, and 

 it confirms the equivalence of the Vicksburgian with the Tongrian. It appears to be 

 exterminated in the Upper Pliocene. 



Variations. This species has not remained exactly identical, throughout its 

 long geologic persistence. The ovicell of the specimens from the English Crag 

 (Pliocene) is hardly costulate: the costules are quite visible and very clear in the 

 French Miocene ; they are finally very salient and quite vigorous in our American 

 specimens. These variations do not seem to us of specific order, for the calcifica- 

 tion of the zoaria depends much on the richness of the waters in lime. 



The restoration which we have attempted (fig. 1) indicates a ramose zoarium 

 branching dichotomously in the same plane; its total length seldom exceeds 3 or 4 

 centimeters. 



The sinus of the apertura shows a small, very fragile lyrtila whose function is 

 unknown for it does not appear identical with the lyrula of Smittina. 



The zooecia are convex (fig. 3) or marginate (fig. 2) ; but always bordered 

 with numerous and triangular, large areolae generally visible in the interior (fig. 6). 



The frontal of the ovicell (fig. 5) is very fragile and moreover often wanting 

 on the fossils. The longitudinal section (fig. 10) is the habitual section of the 

 endozooecial ovicells: the larvae ought to be very large. The orifice of the ovicelled 

 zooecia is three times larger (la=O.W instead of 0.10 mm.)- than the apertura of 

 the ordinary zooecia. The tangential section (fig. 8) shows by its lateral reticula- 

 tions and its sinous median line, the presence of a pleurocyst reposing on the 

 olocyst ; but this appears very thin and is never seen exteriorly. 



1^=0.08 mm. . fs=0.60mm. 



Measurements. Apertura ,, Zooeciai, 



IZa=0.10mm. (fe=0.30-0.3G 



Maximum width of the fronds =2 mm. 



Occurrence. Yicksburgian (Marianna limestone) : One mile north of Mon- 

 roeville, Alabama (very common) : near Claiborne, Monroe County, Alabama (com- 

 mon) ; 2i miles north of Millry, Washington County, Alabama (rare) : Vicksburg, 

 Mississippi (common in the lower beds). 



Geological distribution. Priabonian of Transylvania and Galicia (Pergens). 



Latdorfian of Germany (Reuss, Stoliczka). Rupelian of Germany (Reuss). Chat- 



i inn of Germany (Reuss). Burdigalian of Spain (DeAngelis), of the Gard (Canu). 



Helvetian of Touraine (Michelin). of Spain (DeAngelis). Tortonian of Servia 



(Pergens), of Austria -Hungary (Reuss), of Italy (Seguenza). Sahelian of Oran 



(Coll. Canu). Zancleen of Italy (Seguenza). Plaisancian of Italy (Seguenza, 



Xeviani), of England (Busk), of Belgium (Van den Broeck). Astian of Italy (Se- 



