86 
BULLETIN" 106, UNITED STATES NATIONAL MUSEUM. 
SECTION 1. MEMBRANIPORAE WITHOUT OVICELL. 
Genus CONOPEUM Norman, 1903. 
1903. Conopeum Norman, Natural History of East Finmark, Annals Magazine Natural His- 
tory, ser. 7, vol. 11, p. 5S6 (1S4S, Gray, last British Animals British Museum. Cen- 
troniae, pp. 10S, 146). 
No ovicell. no dietellae, no avicularia. The margins of the mural rim are wholly 
granulated. A distal, multiporous septula; two or three lateral septulae. Tri- 
angular, interopesial hollows having special walls. 
Genotype. — M embranipora lacroixii Authors. 
Range. — Cenomanian-Recent. 
The granulations of the mural rim are often very fine and attenuated on the 
fossil forms. In these also the distal septulae often unite into a very large pore. 
A-D. Conopeum lacroixii Busk, 1852. A. Zooecia, X 25. B. Zooecia, X 25, with intero- 
pesial cavity ( i . c .) ; operculum (op), and opesium (opi). C. Dorsal surface, X 25, showing a 
pair of transparent circles (I. s.=lucid spots of Norman), irregular projections (Ip) on the 
lateral wall, and a pair of projections (d. p.) on the distal wall opposite those on the next 
zooeeium. D. Operculum, X 85, with chitinous arch (ca) and membranous extension (ea). 
(A, B after Hincks, 1S80, and C, D after Waters, 1898.) 
The hollows of the surface are not interzooecial, as Levinsen has described them, 
but are only interopesial; they are not deep and are situated between the mural 
rims; rarely they contain an avicularium; their purpose is unknown. In living 
specimens Waters has described two lucid spots on the dorsal side. These are 
replaced on the fossils by two hollow impressions in the dorsal olocyst. We are 
ignorant of their use, for they have no connection with the operculum. 
The type of this genus is very common on the coasts of France and England, 
and Osburn has noted its occurrence in American waters. However, no naturalist 
has made a study of its embryology and anatomy. 
The known species of this genus, in addition to the genotype, are : 
Conopeum (M embranipora) bravardi Canu, 1911, Kocanean of Argentina. 
Conopeum (M embranipora) arborea Canu, 1911, Kocanean of Argentina. 
Conopemn (M embranipora) langana Canu, 1911, Kocanean of Argentina. 
Conopeum (M embranipora) maplestonei Canu, 1911, Rocanean of Argentina. 
B *25 
Fig. 25. — Genus Conopeum Norman, 1903. 
