278 MOLLUSCOIDEA—BRYOZOA SUB-KINGDOM V 
Family 7. Amplexoporidae. Ulrich. 
Zoaria ramose, encrusting, discoidal, or massive, rarely bifoliate. Zowcial tubes com- 
paratively simple, prismatic, with a well-marked divisional line between adjoining tubes. 
Mesopores practically absent, but small abortive cells sometimes found among the large 
zoacia forming the monticules. Acanthopores generally abundant, sometimes wanting. 
Ordovician to Devonian. 
Amplexopora, Ulrich. Zoaria ramose. Acanthopores always present, varying 
in size and number. Diaphragms 
complete, horizontal. Ordovician to 
Devonian. 
Monotrypella, Ulrich. Like the 
above, but without acanthopores, Ordo- 
vician to Devonian. 
: : Petalotrypa, Leptotrypa, and Discotrypa, 
Fra. 466. Ulrich. Ordovician to Devonian. 
Atactopora maculata, Ulr. Cincinnati, O. Transverse Atactopora, Ulrich (Fig. 466). Zoaria 
and Nera) Caer Unicke Showing -prcaisn pare Ul a thin, growing on Orthoceras.  Zocecial 
apertures indented or floriform, accord- 
ing to position of the very numerous acanthopores. Rather large, solid elevations, 
composed of abortive cells, and completely filled by calcareous deposit, stud the surface 
at regular intervals. Diaphragms thin, few, sometimes wanting. Ordovician. 

Sub-Order C. CRYPTOSTOMATA. Vine. 
Primitive zowciwm short, pyriform to oblong, quadrate, or hexagonal, sometimes tubular, 
the aperture anterior. In the mature colony the aperture is concealed, occurring at the 
bottom of a tubular shaft (“ vestibule”), which may be intersected by straight diaphragms or 
hemisepta, owing to the direct superimposition of layers of polypides. Vestibular shaft 
surrounded by vesicular tissue, or by a solid calcareous deposit ; the external orifice rounded. 
Marsupia and avicularia wanting. 
The Cryptostomata differ from the Trepostomata chiefly in that the ‘‘immature region” 
(primitive cell) is usually much shorter, and the passage to the mature region more abrupt. 
Some of the Cryptostomata are ramose, and have long, thin-walled prismatic tubes in the 
axial region, with or without diaphragms, precisely as in the ramose T’repostomata and Cyclo- 
stomata ; but they are distinguished from the latter by the presence of hemisepta, similar to 
those occurring in the vestibule of Escharopora and Phaenopora, two of the most typical genera 
of the Cryptostomata. That these axial tubes are not of primary importance is shown by such 
genera as Cocloconus, Rhombopora, etc., in whose axial tubes a second layer of zoccia has 
grown over the first. This is a rare condition, and is probably to be attributed to an accidental 
interruption of growth. But, where observable, it is to be noticed that the inner extremities 
of the zocecia of the second layer are not drawn out into tubes like those of the primary set, 
but are short, and in all essential respects like those of Escharopora.* 
The Cryptostomata are probably nothing more than Palaeozoic Chilostomata, differing, 
however, from the typical members of the latter (1) in having neither marsupia nor avicularia ; 
(2) in the much greater deposit of calcareous matter upon the front of the zocecia, thus 
producing the vestibule ; (3) in that successive layers of polypides are often developed, one 
directly over the other, in a continuous tube; and (4) in that whenever a zoarium attains an 
uninterrupted width of more than 8 mm., it exhibits clusters of cells differing more or less, 
either in size or elevation, from the average zocwcia. The last two distinctions are suggestive 
of the Z'’repostomata ; and the presence of a vestibule reminds us of certain Mesozoic and recent 

1 [The almost universal practice has been to accept the presence of tubular zocecia as fully 
demonstrating the Cyclostomatous aflinities of the species producing them. Recent investigations, 
however, show that the mere form of the zocecium cannot be relied upon as a subordinal character 
any more than is the presence of tabulae in a tubular organism a certain indication of an 
Anthozoan. | 
