NO. 1323. STR nCTURAL FEA TUBES OF IIOMOTR YP. i—BASSLER. 577 



occasionally larger expanded fronds occur that do not seem to inoscu- 

 late. Surface with ver}^ distinct clusters of larg-e cells, usually raised 

 into low monticules, but sometimes sharp tubercles. Zooecial apertures 

 angular, direct or nearly so, inclosed by thin walls, seven to eight in 

 2 nnu. Mesopores few, usually restricted to the cell clusters. Acan- 

 thopores seldom showing at the surface, but tangential sections reveal 

 a limited number, best developed in the clusters. Zooecial tubes with 

 walls thin and less crinkled than usual in the axial region and thick- 

 ened slightl}^ in the peripheral region, where a few diaphragms and 

 rather large cystiphragms are developed. 



The characteristic features of this species are its thin walls, compar- 

 atively large zoo^cia, and conspicuous clusters, II. clnclnnatiensis, 

 with which this form might be confused, is distinguished by a different 

 mode of growth, smaller zooecia, less conspicuous clusters, and more 

 abundant mesopores and acanthopores. 



Occurrence. — Rather rare in the Fairmount beds of the Lorraine 

 formation at Covington, Kentuckv, and Cincinnati, Ohio. 



Cat. No. 41741, U.S. N.M. 



HOMOTRYPA PULCHRA, new species. 

 Plate XX, figs. 11-14. 



Zoarium large, consisting of expanded fronds, subdividing or send- 

 ing off other fronds, and ranging from 5 to 10 or more cm. in height; 

 frohds 8 to 5 mm. in thickness and sometimes as much as 8 cm. in 

 width. Surface smooth, the clusters scarcely ever rising above the 

 general surface, but nevertheless conspicuous on account of the large 

 size of their cells. Zooecial apertures thin walled, angular, direct, 

 seven to eight in 2 mm. An occasional mesopore is developed, but 

 only in the clusters. Acanthopores are apparently always wanting, 

 although the thickenings sometimes seen at the angles of junction sim- 

 ulate these structures. Diaphragms from 1 to li tube diameters apart 

 in the axial region and four or live times as numerous in the periph- 

 eral region. C3^stiphragms in an increasingly crowded series in the 

 peripheral region and extending close to the surface. 



This fine species can be readily distinguished externally by its hand- 

 some mode of growth, smooth surface, large and thin-walled zooecia, 

 and conspicuous clusters; internally, by the absence of acanthopores 

 and the unusual development of diaphragms and cj^stiphragms, of which 

 the outermost are commonly visible at the surface. It is scarcely nec- 

 essary to distinguish this from other species. H. curvata bears a slight 

 resemblance in growth, but differs in all other features. 



Occurrence. — A characteristic and common fossil restricted to the 

 Platystrophia lynx horizon of the Mount Auburn beds, Lorraine for- 

 mation, at Cincinnati and Lebanon, Ohio, and other localities. At 

 Cincinnati this lied occupies the tops of the highest hills. 



Cat. Nos. 41747, 41748, U.S.N.M. 



