284 



BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



pores. There are two pairs of lateral dietellae and a distal dietella. The ovicell is 

 hyperstomial and is always closed by the operculum. The avicularia are always 



lumen line 

 Lumen pore- 



FIG. 82. Genus ilenihruitiiivnllii Smitt. 1873. 



A. Mem bran iporeUa ilistans MacGillivray, 188?. A. Zooecium, X 55, showing terminology. 

 (After Levinsen, 1909.) 



B-K. Membraniporella nitida Johnston, 1838. B. Larva, oral face, X 75. C. Aboral viexv 

 of larva, X75. D. Free larva seen in profile, X 100. (B-D after Barrois, 1877.) 

 V. D., digestive cavity. o, mouth of the gastrula. 



ce, obscure portion of the cavity of the body Pit, pharynx, 

 included between the two branches of the rv, border of the terminal bud. 

 stomach. si. furrow separating the terminal bud and the 



ml, aboral mesoderm. lower portion of the nboral face. 



ms, oral mesoderm (labial). 



E. Outline showing the structure of the cell, X 50. (After Hincks, 1880.) 



F, G, H. Various forms of this species. I. Ancestmla. (F-I after Hincks, 1880.) J. Mandible, 

 X 250. K. Operculum, X 85. showing it continuous with the membrane (opprcular valve). 

 (J, K after Waters, 1890.) 



dependent. The aperture is closed by an opercular valve. The larva is that of the 

 Escharines (Ascophora). 



Genotype. Membraniporella (Lepralia} nitida Johnston, 1838. 



Range. Cenomanian-Kecent. 



