NORTH AMERICAN EARLY TERTIARY BRYOZOA. 393 



. [Exterior aperture transverse and mucronate__ _-6. 

 ' | Aperture elliptical 7. 



[Two small lateral avicularia H. transversora. 



''\Two large avicularia below the aperture. .H. ligulatn. 



. | Avicularia very small; zooecia hexagonal H. pungcns. 



'') Large avicularia 8. 



| Lower face smooth or tubercular, two large avicularia -.H. alifcni. 



* [ Lower face of the zoarium perforated; one large and one small avicular'mm_.ff. radicatn. 



.' No mucro 30. 



q J 

 | Mucro present 11. 



fPeristome thin; two large nvicularia, ovicell smooth ._ H. ulifcra. 



10. jPeristome thin; one submedian avicularium, ovicell with small pores II. punctata. 



Iperistome very thick; two or three small avicularia; ovicell smooth H. crassicollis. 



[Two large avicularia H. ligulnta. 



(Two small avicularia-- _ 12. 



[Enormous mucro with pallet; three rows of areolae H. axiculata. 



'"[Small mucro; tuberosities radial on the frontal H. tuberosa. 



Genus HIPPODIPLOSIA Canu, 1916. 



1916. Hippodiplosia CANU, Les Bryozoaires du Sud Quest de la France, Bulletin SocieK- 

 Geologique France, ser. 4, vol. 14, p. 326. 



The poster is nearly as large as the anter. The operculum is somewhat nar- 

 rowed laterally at the site of the cardelles. The operculum always closes the ovicell, 

 which is hyperstomial. The frontal is a tremocyst. There are some spines and 

 some avicularia. 16-18 tentacles. 



Genotype. Hippodiplosia (Eschara) pallasiana Moll, 1803. 



Range. Jacksonian-Eecent. 



In this genus the vanna is very large ; it is the opening of a compensation sac, 

 probably larger than in Hippoporina Neviani, 1895. Consequently the tentacles 

 ought to be more numerous or larger. Calvet reports 16 to 17 tentacles in the 

 genotype. On the other hand, one can suppose that a larger vanna permits simply 

 more rapid egress of the tentacles as an immediate compensation, since the com- 

 pensatrix is smaller in this group than in Schizoporclla. 



The Eocene species of the genus are rather different from those of the Miocene. 

 It is probable that when the physiology of the avicularia is better known some 

 restrictions will be necessary. 



The living species of this genus are : 



Hippodiplosia (Eschara) pallasiana Moll, 1803. 



Hippodiplosia (Lepralia) vestita Hincks, 1885. 



The fossil species are: 



Hippodiplosia (Lepralia) rarepuncta Reuss, 1847. Tortonian. 



Hippodiplosia (Lepralia) planiceps Reuss, 1847. Tortonian. 



Ilippodiploxia (Lepralia) semieristata Reuss, 1847. Tortonian. 



Hippodiplosia (Lepralia) clavata. Manzoni, 1874. Tortonian. 



Hippodiplosia (Leprnlia) auingcri Reuss, 1847. Tortonian. 



