270 



BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



TREMATOPORA KUCKERSIANA, new species. 



Text fig. 159. 



Free examples of this fine new form have not been seen, the species 

 being founded upon specimens embedded in the soHd Hmestone. 

 These, however, are well preserved and show the following char- 

 acters : 



Zoarium of cylindrical branches 5 mm. in diameter, dividing infre- 

 quently. Surface smooth, with the usual maculae of large zooecia 

 and wider interspaces. Zooecial apertures rounded to oval, with a 

 well-marked peristome. Six to seven zocecia in 2 mm., measuring 

 from the center of a macula. Acanthopores few. Mesopores numer- 

 ous, usually isolating the zooecia, but not visible at the surface where 

 their place is taken by tissue forming the solid interzooecial spaces 

 characteristic of the genus. 



Fig. 159.— Tkematopoea kuckeksiana. a, tangential section, X20, showing oval zocecia and 



DISTINCT peristomes; 6, VERTICAL SECTION, X20; C, ANOTHER VERTICAL SECTION, X20, SHOWING THE 

 BEADED MESOPORES WITH CYSTLIKE DIAPHRAGMS. KUCKERS SHALE (C2), REVAL, ESTHONIA. 



Vertical sections show the usual beaded mesopores with numerous 

 diaphragms, which, when unusually crowded, give a cystose structure 

 to the interzooecial spaces. As the surface is approached the meso- 

 pores become filled with a laminated tissue, which, in tangential or 

 surface views, appears as solid interspaces. The zooecia have thin 

 walls and no diaphragms in the immature region and slightly thick- 

 ened walls with only an occasional diaphragm in the mature zone. 

 The beaded mesopores, with their crowded, often cyst-like diaphragms, 

 and their outer filling of tissue, form the most important feature of 

 such sections. 



Tangential sections through the outermost part of the zoarium show 

 oval to circular zooecia with distinct peristomes separated by solid 

 tissue, through which the outlines of the mesopores are sometimes 

 faintly visible. Deeper sections exhibit the mesopores more clearly, 

 but show less distinct peristomes. 



