NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



419 



FIG. 123. Anatomy nf Hit' Mieroporellae. 



A-E. Micropurclla ciliatu I'allas. 1VGU. A. Profile view of free larva, X 75. B. Free 

 larva, oral view, showing the large radiating elements of the oral mesoderm. X 50. C. Free 

 larva, aboral view, showing the radiating aspect of the calotte, 50. (A-C after P.arrois, 1877.) 



ms, oral mesoderm ; 



<>. dilated cleft; 



oc, oculiform points ; 



////, pharynx ; 



JfV, horder of the calotte. 



c, corona ; 



c/. calotte (terminal bud); 



CD. digestive cavity; 



, obscure part between the two branches of 



the stomach ; 

 mi. ahoral mesoderm; 



D. Median sagittal section of an embryo in one of the last stages of development. (After 

 Calvet, 1900.) E. Ancestrula and two zooocia. The original aperture of the ancestrula. which 

 is surrounded by spines, is almost closed to a pore, X 5o. (After'Levinsen, 1909.) 



F-N. Microporella malusi Audouin, 1S26. F. Median sagittal section of an embryo just 

 before it emerges. (After Calvet. ItiOO. ( In the course of the neuro-muscular bundles passing 

 from the central nerve organs to the pyriform organ some cellules are seen. The internal sack 

 has a simple form almost regularly c-ylindrical. 



c. mantle; fum. neuro-muscular bundle; 



cal, calotte ( terminal bvicl ) ; one, central nervous organ of the embryo ; 



co, corona; pfse, sub-ectoderm nerve plexus; 



d, tampon or inner sac; pplt; papilla of the vibratile plume; 

 ect, ectoderm; si, internal sac; 



eye, ectoderm thickening; scis, superior glandular system; 



I'pin. mesoderm thickening; .,71. inferior glandular system. 



fc, ciliated cleft ; 



G. Longitudinal section of a bryozoid. (After Calvet, 1900.) 



i 'a i. stomachic caecum; 



ft. incubation cavity ; 



cry. cryptocyst. or skeleton 



d, diaphragm ; 



cph, hypostegal epithelium 



epi, spine; 



fc, central funicular cord: 



fl, lateral funicular cord ; 



fin. nervous ganglion; 



fit, sub-diaphragm region 



sheath ; 



(if, subrliaphragm region; 

 liii. liypostege; 



H. Zooecia, X 50. (After Wad r>. 



of the tentacular 



mud, dilator muscles of the incubation cavity ; 



in H fir. large retractor muscle; 



/ni: retractor muscles of the frontal walls 



of the lower ovlcellarian vesicle ; 

 ocs, esophagus : 

 op, operculum ; 

 ox. zooecial orifice ; 

 lime, median frontal pore: 

 pit. pyloris ; 

 rr, rectum : 

 /, tentacles ; 



roi. lower ovicellarian vesicle ; 

 ms, upper ovicellarian vesicle. 

 I. Ancestrula. The frontal membrane (fin) 



1903.) 



is typically flustrine and bears an oprrcular valve; its calcareous margin bears ten spines, of 

 which three are oral spines (op). The brown body (hft) may be noted. (After Harmer, 1902.) 

 J. Frontal pores, X 250. (After Waters. 1914.1 K. Aperture, X 100. (After Levinsen, 1909.) 

 L. Basal view of a zooecium which has lost its polypide. (After Ilarmer. 1902.) 

 '. polypide bud; n-l. opercular muscles; 



lii:. brown body; p. c.. dietellae : 



corn, cornicula : ~. neighboring zooecia. 



< g, rompensatrix opening by the ascopor" 

 (m. p.) : 



