766 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Affinities. The ovicelled specimen (fig. 4) bears two ovicells symmetrically 

 placed to the right and left of the zoarium. 



This species differs from Plcuronca alvcolota in the fibrous aspect of the basal 

 lamella and in the different position of the ovicell. 



It differs from Plcuronca- (Idmonea) fenestrata Busk. 1859, in its much smaller 

 tergopores and its smaller micrometric measurements. 



Occurrence. Midwayan (Clayton limestone) : Luverne, Crenshaw County, 

 Alabama (common). 



dotijpes.G&t. No. 65244, U.S.N.M. 



PLEURONEA FENESTRATA Busk. 1859. 



Flute 114, figs. 1-1S. 



1859. Iiliiuinca fan-strata BUSK, A Monograph of the Fossil Folyzoa of the Crag, Publi- 

 cations of the Falaeontographical Society of London, vol. 14, p. 105, pi. 15, fig. 6. 



1877. Idmonea fenestrata MANZONI, I Briozoi fossili del Miocene d' Austria ed Ungheria; 

 Part 3, Denkschriften der math, natur. Classe der k. Akademie der Wissenschaften 

 Wien, vol. 38, Abth. 2, p. 6, pi. 4, fig. 14. 



1SSO. Idmonea fenestrata SEGUENZA, Le formazioni terziarie nella Provineia di Reggio 

 (Calabria), Reale Accademie del Lincei, Memoire della Classe cli Scieuze Fisiche 

 niateinatiche e Natural!, Roina, ser. 3, vol. 6, p. 132. 



1897. Idmonea fenestrata NEVIANI, Corallari e Briozoi neogenici di Sardegna, Bolletino 

 dell Societa Geologica Italiaua, Ronia, vol. 15, p. 595 (27). 



Description. The zoarium is free, arborescent, bifurcated or reticulated with 

 oval section, idmoneiform. The fascicles are quite salient, uniserial, scattered, 

 alternate, adjacent to the median crest. They bear at the maximum five tubes. 

 The tubes are salient, visible exteriorly, flat, separated by a salient thread; the 

 peristonie is thin and rectangular. The basal lamella bears a thick layer of tergo- 

 pores almost as large as the tubes; their orifice forms regular, longitudinal lines 

 or a complicated network. The ovicell is large, convex, porous; it bears tuberosi- 

 ties arranged in quincunx. 



(Peristome 0.12 mm. 



Measurements. { Distance between the fascicles 0.24-0.30 mm. 



Variations. The basal side of this species is quite variable; there is not a 

 single specimen exactly like the others. The orifices of the tergopores are large 

 (fig. 4) or small (figs. 5, 7, 13) in quincunx or in lines; they even overturn the 

 frontal on the old zoaria (figs. 12, 16); those which are arranged in longitudinal 

 series are the most frequent. The tergopores sometimes occur at the base of pseudo- 

 sulci. 



Fortunately the frontal is more regular (figs. 3, 14) and permits the determi- 

 nation more easily. 



The ovicell of this species is quite variable in its form, dimensions, and posi- 

 tion. In our studies on the cyclostomatous bryozoa we figure some interesting 

 variations which show that the ovicell is as polymorphic as in the genus Tubuli- 

 pora itself. 



