﻿42 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



In tangential sections the walls present the sharply-defined median 

 line separating adjoining zooecia characteristic of the family Amplexo- 

 poridce. In deep sections the walls are extremely thin and the acan- 

 thopores very small. Vertical sections show repetitions of immature 

 and mature regions, the former being distinguished by thin walls and 

 diaphragms a tube diameter or more apart, the latter by appreciably 

 thickened walls and more crowded diaphragms. In the mature 

 regions many of the diaphragms are further distinguished by being 

 recurved, usually from one wall only, but not infrequently from both 

 sides, the structures in the latter case being infundibuliform. 



The zocecia in this fine species are larger than in any other now 

 referred to this genus, and this feature, in connection with the pres- 

 ence of recurved and funnel-shaped diaphragms, distinguishes this 

 form from all other massive or discoid species of the genus. 



Occurrence. — This is one of the most characteristic species of the 

 Lorraine formation in the Central Basin of Tennessee. The types 

 are from the top of Mt. Parnassus at Columbia, Tennessee, although 

 many other localities in Maury and other counties furnish an abun- 

 dance of specimens. 



Cat. Nos. 43,210-43,212, U. S. N. M. 



AMPLEXOPORA AMPLA new species 



(Plate XIII, 7, 8; Plate XIV, 3) 



In size of zocecia this species agrees fairly well with the preceding, 

 with which it is also generally associated, but the two are readily dis- 

 tinguished by their different methods of growth. In the hundreds 

 of specimens observed A. columbiana is always massive, while A. 

 amp la adheres as strictly to the ramose habit of growth. Its 

 branches are smooth, divide frequently, and are usually about 10 

 mm. in diameter. The zocecia are large, about 7 in 2 mm., with sub- 

 angular apertures and rather thin walls. The acanthopores are 

 small and so far have been observed only in thin sections. They 

 seem never to reach the size of those in A. columbiana. Diaphragms 

 occur at intervals of several tube-diameters in the axial region, but 

 in the peripheral they are much more abundant, many of them lure 

 also being funnel-shaped. 



./. ampla is closely related to A. cingulata I'lrich, the type spe- 

 cies of the genus, but has larger zocecia and fewer acanthopores. 



Occurrence. — Abundant in the Lorraine formation at Nashville 

 and Columbia, and many other localities in Tennessee, where these 

 strata are exposed. Rather rare in the Fairmount beds of the Lor- 

 raine at Cincinnati, Ohio, and vicinity. 



Cat. Nos. 43,213-43,215, U. S. X. A I. 



