398 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



D'Orbigny, 1852, has described as Lanceopora. Unfortunately the 

 genotype no longer exists at the Paris Museum and as the French 

 author described a round aperture we can not with certainty establish 

 the synonymy. We retain therefore the name of Maplestone. 



Structure. — The zooecial form is very special; on the interior, it 

 appears lozenge-shaped, but the walls are arched and parallel two by 

 two. This arrangement is absolutely different from that of other 

 bilamellar cheilostomes. As a consequence, the aperture undergoes 

 the same deviation; it is not oriented in the apparent linear axis of 

 the zooecium but is oriented in the curved axis of the latter. 



The mode of gemmation is altogether special. The zooecia of the 

 two axial rows of each segment are arranged normally. They are 



Fig. 154. — Genus Hippopodinella Barroso, 1924 



A-F. Hippopodinella adpressa Busk, 1854. A. Zooecia without tuberosities 

 X30. B. Zooecia with tuberosities X30. C. A zooecium showing the endo- 

 zooecial ovicell. (A-C. After Hincks, 1880.) D. Operculum, X140. E. 

 Different aspects presented by the marginal cavities when the zooecium is viewed 

 from the dorsal side. F. Ovicelled zooecium decalcified, viewed from the dorsal 

 side; e, embryo; em, mesenchymatous elements; mo, opercular muscles; mp, 

 parietal muscles; mr, retractor muscles. (D-F. After Barroso, 1924.) 



alternate and engender a distal zooecium and a lateral zooecium. 

 All the other zooecia engender only a lateral zooecium. The general 

 growth is therefore peripheral and the basal lamella (germinale 

 lamella of D'Orbigny) entirely surrounds the segment. In all other 

 cheilostomes this lamella is always terminal. 



"The zoarium is furnished with a long flexible stem or filament 

 some 6 or 7 cm. long and. 2 mm. thick, upon the summit of which the 

 zoarium is attached. The point of attachment is at the curved 

 indentation in the center of the lower margin of the zoarium. The 



