586 PROCEEDINGS OF THE NATIONAL MUSEUM. voL.xxvi.i 



with low broad monticules, the center of each usually occupied by a 

 star-like cluster composed of mesopores only and surrounded by cells 

 slio-htly larger than the averao-e. Apertures polygonal, direct, ten to 

 eleven in 2 mm. Mesopores restricted almost entirely to the clusters.,; 

 Acanthopores few and rather small, although now and then one ofl 

 large size may be present, and these in vertical sections have thini 

 transverse partitions. Diaphragms are developed in the zooecial tubes, 

 as the peripheral region is approached and are quite numerous neari 

 the surface. Cystiphragms of rather small size line the tubes as usual' 

 in the peripheral region; in a tangential section they appear much less 

 curved than is generally the case, sometimes showing as a straight 

 line across the cell cavity. i| 



The small cells and much branched growth externally, and thei' 

 strong development of both diaphragms and cystiphragms in the 

 pei'iphei'al region, are characteristics which readily distinguish this: 

 form from other Richmond species. 



Occwrrence. — Middle division of the Richmond formation at Ver-j 

 sailles, Indiana. 



Cat. No. 41760, U.S.N.M. 



HOMOTRYPA NITIDA, new species. 

 Plate XX, fig. 15; plate XXV, fig. 5-8. 



Zoarimn of small, frequently branching, more or less cylindrica 

 stems, usually 4 or 5 mm. in diameter. Surface smooth. Macula 

 large, composed of zooecia, which are often twice the diameter of th( 

 ordinary cells; 10 zooecia in 2 mm. Diaphragms few in the axia 

 region, not very abundant in the peripheral region, where also the 

 cystiphragms are large but not abundant. Acanthopores small, few'j 

 usually wanting. \ 



This species is closely related to 11. gelasinosa, and may be onljl 

 a variety of that form. The larger maculaj and acanthopores anc 

 llabellate growth of the latter are deemed of sufficient value to dis 

 tinguish it from H. nitlda. 



Occtirrence. — Richmond formation, near Osgood, Indiana. 



Cat. No. 41771, U.S.N.M. 



HOMOTRYPA NICKLESI, new species. 



Plate XXII, figs. 4-7. 



In growth and external features this species resembles H. comm unis 

 but is readily distinguished by the less robust growth and the tendency 

 to branch more frequently. The internal structure further distin 

 guishes the two, since //. nicklesi is of the II. curvata group, while II 

 communis is of the group to which it gives its name. Surface smooth 

 with regularly disposed maculae of larger cells and mesopores. Zooeci; 



