288 MOLLUSCOIDEA—BRYOZOA SUB-KINGDOM V 
Family 10. Microporellidae. Hincks. 
Zoaria encrusting or erect, foliated or dendroid. Zowcial orifice more or less semi- 
circular, with the lower margin entire; a crescentic or 
circular pore on the front wall usually just beneath the 
orifice. Cretaceous to Recent. 
Microporella, Hincks (Fig. 482). Zoarium encrusting 
or erect, bilaminar. Margin of zocecia not elevated. 
Orifice with a straight, entire lower border, frequently 
with oval spines. Usually one semi-lunate or circular 
pore beneath the orifice, occasionally two or three. 
Tertiary and Recent. 
Diporula, Chorizopora, Hincks, Tertiary and Recent. 
? Monoporella, Hincks. Like Microporella, but with- 
out special pores. Cretaceous to Recent. 

Fia. 482. 
Microporella rudis, Reuss sp. : ako - : 
Oligocene; Sdllingen. Upper sur. Family 11. Porinidae. d’Orbigny, emend. Hincks. 
face, enlarged. 
Zoaria encrusting, or erect and ramified. Zowcia with 
a raised tubular or sub-tubular orifice, and frequently with a special pore on the front wall. 
Cretaceous to Recent. 
Porina, VOrb. Zoaria consisting of flattened or sub-cylindrical branches, celluli- 
ferous on both sides, or encrusting. With age the spaces between the raised apertures 
become filled with a porous calcareous deposit. Avicularia and ocecia occasionally 
distinguishable. Cretaceous to Recent. 
Celleporella, Gray ; Anarthropora, Smitt ; Lagenipora, Hincks. Recent. 
Family 12. HEscharidae. Hincks. 
Zoaria erect, unilaminate or bilaminate, foliaceous or ramose, or crustaceous, loosely 
attached or adnate. Zowcia urceolate, the front entirely calcified, without raised margins. 
Orifice anterior, sub-circular to horseshoe-shaped, the lower border straight, broadly sinuate, or 
notched. An elevated secondary orifice, with the lower margin dentate, channeled, or 
enclosing an avicularium, often present, but no special pores. Cretaceous to Recent. 
This family embraces a large number of fossil and existing Bryozoans, and in its present 
state can hardly be said to form a natural group. It is here that the much greater importance 
of zocecial characters as compared with zoarial are particularly apparent ; inasmuch as one genus, 
or in many cases a species, as now generally understood, may include a considerable range of 
zoarial types. To the palaeontologist the group offers exceptional difficulties, since generic 
characters frequently depend upon easily abraded or obscure modifications of the orifice. 
Lepralia, Johnston (Fig. 483). Zoaria encrusting or rising into simple or branching 
expansions, composed of one or two layers of cells. Zocecia usually ovate, the orifice 
with a thin peristome and entire lower margin. Rare in Cretaceous, more abundant 
in Tertiary and Recent. 
Porella, Gray, Zoaria encrusting or erect. Zocecia with a semi-circular primary 
orifice ; the secondary (adult) orifice elongate, inversely sub-triangular, or horseshoe- 
shaped, and enclosing an avicularium with a rounded or sub-triangular mandible, 
Tertiary and Recent. 
Smittia, Hincks. Zoaria encrusting, or erect and foliaceous. Primary orifice of 
zocecia sub-orbicular, the lower margin with an internal median denticle. Secondary 
orifice canaliculate below ; generally a small avicularium either within or just beneath 
the sinus. Miocene and Recent. 
Mucronella, Hincks (Fig. 484). Similar to Smittia, but with simpler orifice, and 
