fo.l323. STRUCTURAL FEATURES OF HOMOTRYPA—BASSLER. 575 



DESCRIPTIONS OF SPECIES. 

 HOMOTRYPA CURVATA Ulrich.a 



Ilomoti-ypa curvata Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, 1882, p. 242, 

 ^pl. X, figs. 7-7d. 



In growth this species is between the cylindrically ramose species 

 ind the truly frondesccnt forms as 77. Jlahelhiris. Acanthopores, 

 iystiphragms, and diaphragms are present in a moderate degree. The 

 ixternal characters by which the species may be recognized are the 

 compressed, flattened branches and smooth surface; in thin sections, 

 by the average number of acanthopores (three or four surrounding a 

 30oecium), absence of mesopores except in the macule, ten zooecia in 

 2i mm., the presence of diaphragms in the axial region, and of both 

 diaphragms and (33^stiphragms in the peripheral region. 



Occurrence. —A common and characteristic fossil in the Fairmount 

 beds of the Lorraine at Cincinnati, Ohio, and vicinity. 



Cat. Nos. 41729-41734, U.S.N.M. 



HOMOTRYPA CURVATA var. PR.ffiCIPTA, new variety. 

 Plate XXIII, fig. 15. 



This varietal name is proposed for the only Honwtrypa known in 

 the Utica. It has the internal characters of 77 curvata^ but differs in 

 the growth of the zoarium. Its branches are cylindrical, smooth, 

 about 6 mm. in diameter, and divide at short intervals, while the 

 zoarium of 77 curvata takes the form of broad, compressed branches, 

 dividing at less frequent intervals. Thin sections show that the Utica 

 form generall}' exhibits more acanthopores, but the number of acan- 

 thopores varies slightly in every species. 



Occurrence. — Rare in the middle division of the Utica at West 

 Covington, Kentucky. Cumings^ records the same form from the 

 Upper Utica. 



Cat. No. 41735, U.S.N.M. 



HOMOTRYPA OBLIQUA Ulrich. 



Plate XXIII, figs. 12-14. 



Homotrypa ohliqua Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, 1882, p. 243, 

 pi. X, figs. 6-6b. 



This abundant Lorraine species in its internal characters is very 

 much like II. curvata. The absence of diaphragms and the slightly 

 crinkled walls in the axial region distinguish it from H. curvata. 



<" Under species heretofore described, the reference to the original description only 

 is given. The complete synonymy is presented in Bulletin No. 173, U. S. Geological 

 Survey, 1900. 



^American Geologist, XXIX, 1902, p. 215, footnote. 



