456 



The thin parasitic growth and markedly hexagonal cells are 

 the most noticeable features of this species. 



Position and locality: Trenton group, Mineral Point, Wis.; 

 Calhoun Co., 111.; and Minneapolis, Minn. 



LEPTOTEYPA FILIOSA D'Orbigny. 



PL XXXVI, Fig. 7-7a. 



Monticuliporafiliosa D'Orb., 1850. Prod, de Pal. t. I, p. 25. 

 Chcetetes ftliosa Ed. & H., 1851. Pol. Foss des Terr. Pal, p. 261. 

 Chcetetes filiosa ? Nich., 1875. Pal. Ohio. vol. II, p. 206. 



This species is a very common one in the Cincinnati group at 

 Cincinnati, Ohio. It is massive in shape, sometimes attaining 

 a vertical thickness of thirty cm. or even more. The zooecial 

 tubes are regularly prismatic, seven or eight in two mm., with 

 groups of larger size. Diaphragms something over a tube 

 diameter apart, but become about twice as close-set as the 

 zooecial tubes near the top of a mature region. Acanthopores 

 few and inconspicuous, only present in the mature regions, 

 therefore only rarely met with in tangential sections. Mature 

 region very short. Many successive mature and immature 

 regions may be observed upon some specimens, the tubes usually 

 being continuous throughout the. zoarium. The sections figured 

 were taken from a small specimen from the Trenton group of 

 Calhoun Co., 111. This is the first time this species lias been re- 

 corded from so low a horizon. 



LEPTOTEYPA STIDHAMI Ulrich. 



PL XXXVI, Fig. 4-4b. 



Zoarium irregularly lobate-massive. Surface smooth, with 

 clusters of somewhat larger cell apertures. Zooecial tubes radiat- 

 ing out in all directions from a point in the base, angular, 

 irregular in shape, and thin-walled even to the surface, from 

 eight to ten in two mm. Diaphragms horizontal, about a tube 

 diameter apart. Acanthopores ra.ther large, numerous, situated 

 at the angles of the zooecia. 



The shape of the zoarium and the number and regularity of 

 the diaphragms, combined with the size and number of acantho- 

 pores, are the main distinguishing features of this species. 



