NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
281 
are the lateral lacunae; the openings developed at the extremities are median 
lacunae. A lateral lacuna consists then of two parts divided horizontally (E), 
taking their origin in the lateral walls of two adjacent costules. A median lacuna 
consists of two vertical portions formed by the distal extremities of two opposite 
costules (F). 
Classification. — For the reception of species of this family, D’Orbigny in 1852 
created the two families of Escharellidae (without avicularia) and Eschariporidae 
(with avicularia). These names prevailed for 30 years. 
In 1880 Hinclcs showed that Cribrilina Gray, 1848, has priority over Eschari- 
pora D’Orbigny, 1852, and made this genus the type of the Cribrilinidae. 
In 1886 J. Jullien 1 established that Membraniporella was not a true member 
of the Cribrilinidae. Thus regarding the family of Hincks in a different sense, 
especially since he added to it the Steginoporidae D'Orbigny, he gave it another 
name — the Costulidae. 
The classification adopted by the French author is based chiefly on the form 
of the aperture and on the development of the oral spines. Most of his genera may 
be preserved with some modification 
of diagnosis. 
In 1909 Levinsen established 
that Hincks’ family was not nat- 
ural, that certain genera have affini- 
ties with the Anasca and others with 
the Ascophora. 
Our studies of the American 
bryozoa confirm Levinsen’s views, 
but we can not discover the true 
affinities of each genus, because it is from the larva alone that these can be dem- 
onstrated. The attention of the zoologists is called to this, as well as to the great 
number of other unsolved problems in the science of bryozoology. 
Spines more or less joined together occur in the genus /ScrupoceUaria and in 
the family Catenicellidae. but the formation of the costules is the enigma of 
bryozoology. 
The accompanying figures give a summary of the principal genera known in this 
so-called family. 
Genus MEMBRANIPORELLA Smitt, 1873. 
1873. Membraniporella Smitt, Floridan Bryozoa, Kongl. Svenska Vetenskaps-Akademiens 
Handlingar, vol. 10, No. 11, p. 10. 
Bibliography ( anatomical ). — 1877. Barrois, Recherches sur T embryologic des Bryozoaires, 
pi. 8, figs. 27, 29, 32. — 1899. Waters, Bryozoa from Madeira, Journal of the Royal Micro- 
scopical Society, pi. 3, figs. 18. 19. — 1903. G. Norman, Notes on the Natural History of East 
Finmark, Annals Magazine Natural History, ser. 7. vol. 12, pi. 8, fig. 8. — 1909. Levinsen, 
Morphological and Systematic Studies on the Clieilostomatous Bryozoa, pi. 9, fig. 9. 
The costules are provided with a large lumen of greater or less size, without 
pores, and are completely joined or are separated by long slits; usually no lumen 
1 Tke Costulidae, Bulletin de la SoeFtd Zoologique de France, vol. 11, p. 2. 
Fig. 80. — Sketch showing structure of a costule. (Af- 
ter Norman, 1903.) 
