BRYOZOA. 483 



the most striking differences (see PI. LXXYI, fig. 96, and PI. 

 LXXYII, fig. 7b). Thus the zocpcial tubes in Dichotrypa are re- 

 cumbent on the median lamina, then bending outward abruptly 

 proceed direct to the surface. A more or less developed superior 

 hemiseptum is usually recognizable, but diaphragms are absent. 

 On the other hand in Meekopora the tubes are gently curved 

 throughout their length from the median laminae to their aper- 

 tures withe ut becoming direct and, while hemisepta are wanting, 

 numerous diaphragms are present. Other important differences 

 might be pointed out, but as they will be obvious enough to 

 the student, the above are deemed sufficient for the present. 



Four species are now referred to the genus, one of them pro- 

 visionally. Beside these my cabinet contains three more. All 

 the species now positively known to have the structure of the 

 genus are from Lower Carboniferous deposits. 



MEEKOPORA EXIMIA Ulrich. 



PL LXXVH, flg. 6-d. 



Zoarium a bifoliate, somewhat undulating, palmate expan- 

 sion, several cm. in width and two to five mm. in thickness. 

 Surface presenting large, slightly elevated, oval, smooth spots 

 or macuUp. arranged in somewhat regular diagonal rows, five 

 or six mm. apart. The apertures immediately surrounding the 

 macula^ a little larger than the others. Apertures in rather 

 regular oblique rows, all facing up toward the distal part of 

 the zoarium, sub-triangular or semicircular in outline, with 

 prominent overarching lunarial hoods; six or seven apertures 

 in three mm., each with a diameter of about 0.21. Ooecia few, 

 taking the place of one of the zooecia and consisting of a cyst- 

 oid elevation of the surface, with a small perforation at the 

 apex. . Zooecial tubes thin walled, extending with a gradual 

 curve to the surface, without, however, becoming direct. Lu- 

 narium usually obsolete in tangential sections, but sometimes 

 the ends project slightly into the visceral cavity. The axial 

 plane consists of two very thin closely adhering flexuous epi- 

 thecal membranes. Yesicles of irregular shape, much the larg- 

 est near the axial plane, often exhibiting an obscure concentric 



